Defence giant BAE Systems is to axe 1,775 jobs across its naval ships business and end shipbuilding at one the country's most historic yards.

The firm said 940 jobs will be lost in Portsmouth, on the south coast, and a further 835 in Glasgow, Rosyth and Filton, near Bristol.

Shipbuilding operations will end in Portsmouth in the second half of next year, but an engineering team will be retained to support the new Type 26 warships, which will be built in Glasgow.

BAE said it remained committed to continued investment in Portsmouth as the centre of its maritime services and high-end naval equipment and combat systems businesses.

BAE said it was being hit by a "significant" reduction in workload following the peak of activity on the current aircraft carrier programme.

The grim news was given to workers at a series of meetings at 11am across the affected sites, before they were allowed to go home for the rest of the day.

David Hulse, GMB national officer and chair of the Confederation of Shipbuilding and Engineering Unions' (CSEU) shipbuilding national committee, said: "Following today's announcement from BAE Systems, we are able to confirm that no shipyard will be closing even though there are substantial job losses in the pipeline.

"There is no doubt that this is a devastating day for the UK shipbuilding industry and the company will have justify to us the job losses planned.

"We have arranged a two-day meeting with the company at Farnborough next Monday and Tuesday that will be attended by officers and shop stewards from all the yards and all the unions. This meeting will examine in detail the business case and all aspects for scheduling work in the yards to complete building the carriers, starting work on the Type 26 ships and any other work."

Hugh Scullion, general secretary of the CSEU, said: "The CSEU has been assured that further discussions will take place in the coming weeks with BAE over the future of its marine division, which has huge strategic importance for the UK's defence industry.

"Getting an agreement which avoids the need for compulsory redundancies will be central to our discussions with the company. The CSEU will also make it a priority to protect the future of the UK shipbuilding industry by securing investment to ensure the industry doesn't just survive but prospers in the future. "

BAE said: "Following detailed discussions about how best to sustain the long-term capability to deliver complex warships, BAE Systems has agreed with the UK Ministry of Defence that Glasgow would be the most effective location for the manufacture of the future Type 26 ships.

"Consequently, and subject to consultation with trade union representatives, the company proposes to consolidate its shipbuilding operations in Glasgow with investments in facilities to create a world-class capability, positioning it to deliver an affordable Type 26 programme for the Royal Navy.

"The cost of the restructuring will be borne by the Ministry of Defence. The implementation of these restructuring activities will sustain BAE Systems' capability to deliver complex warships for the Royal Navy and secure the employment of thousands of highly skilled employees across the UK.

"In 2009, BAE Systems entered into a terms of business agreement (ToBA) with the Ministry of Defence that provided an overarching framework for significant naval shipbuilding efficiency improvements in exchange for commitments to fund rationalisation and sustainment of capability in the sector.

"The agreements announced today, together with an anticipated contract for the design and manufacture of the Type 26 Global Combat Ships programme, will progressively replace that ToBA."

Steve Murphy, general secretary of construction workers union Ucatt, said: "Once again workers have found out that their jobs are under threat through the media. It is highly distressing and extremely unfair to treat a loyal workforce in such a way.

"This is a highly skilled workforce, so it is absolutely essential that the Government and BAE Systems minimises job losses, guarantees the long-term future of all the shipyards and continues to invest in training the workers of the future."

Unite national officer for shipbuilding Ian Waddell said: "This is a very worrying time for the workforces and their families as the work on the two carriers comes to a conclusion.

"Unite will be working very hard to retain the maximum number of jobs at both Portsmouth and in Scotland.

"It is a huge blow to Britain's manufacturing and industrial base, with many highly skilled workers faced with losing their jobs.

"We will have to examine the BAE business case in detail to see how we can secure a future for the workforces at both Portsmouth and in Scotland. We believe that, if this is approached in a constructive and innovative way, it can be achieved.

"The seeds for this situation were sown in the 1980s when the Thatcher government used European structural funds to close shipyards, rather than funding investment that would have allowed Britain to compete in the global marketplace for shipbuilding orders against the likes of South Korea."

Gerald Vernon-Jackson, leader of Portsmouth City Council, said: "I condemn the decision to shut down the last remaining shipyard in England with the capability to build advanced surface warships.

"This decision is bad for Portsmouth, with the loss of many highly-skilled jobs, but it's also bad for the defence of the UK and for the Royal Navy.

"The remaining yards with the capability to build advanced warships are in Scotland, and the referendum on Scottish independence is less than one year away. Ministers have put the defence of the UK and the future of the navy at real risk.

"We will work as hard as we can to protect jobs in Portsmouth. Portsmouth remains the home of the Royal Navy, with more than 10,000 jobs remaining in the dockyard."

Defence Secretary Philip Hammond will address MPs on the future of shipbuilding at 12.30pm, said Downing Street.

Prime Minister David Cameron's official spokesman told a regular Westminster media briefing: "These are decisions taken in the UK's national interest."

Asked whether the desire to encourage Scots to vote No in next year's independence referendum had played any part in the decision, the spokesman said: "This is a Government that always takes decisions based on the national interest.

"This decision was taken with a view of how we have the best-equipped, best-maintained Royal Navy. That is the basis on which it was taken."

Asked whether any contingency plans had been made to preserve shipbuilding capacity in the rump UK in the case of Scotland voting for independence, the spokesman said: "The basis on which we proceed is on the basis that we are confident that the case (for Scotland to stay in the UK) will be successfully made."

The consequence of the decision was that "we have Portsmouth as the home of the Royal Navy fleet... and world-class shipbuilding of Royal Navy ships continuing on the Clyde", said the spokesman.

The MoD announced it is to commission three new ocean-going offshore patrol vessels for the Royal Navy, to be built by the BAE yards on the Clyde in Scotland.

The deal provides work for the company between the completion of the current aircraft carrier contract and the start of the Type 26.

Mr Hammond also announced that more than £100 million will be invested in the naval base at Portsmouth, which will be home to both HMS Queen Elizabeth and HMS Prince of Wales.

The money will expand the dockyard so it is ready for the ships, as well as the Type 45 destroyers which are based in Portsmouth.

Mr Hammond said: "This deal will provide the Royal Navy with three brand-new maritime patrol vessels with a wide range of capabilities which will support our national interests and those of our overseas territories.

"This is an investment not only in three ships but in this country's warship building industry. It prevents workers standing idle and sustains the vital skills needed to build the planned Type 26 frigate in the future.

"I am also pleased to announce additional investment in Portsmouth Naval Base to prepare for the significant increase in tonnage as the home port for the Royal Navy's aircraft carriers and destroyers."

Admiral Sir George Zambellas, First Sea Lord, said: "These new patrol vessels will build on the proven performance of the River Class by adding a flight deck to take the Navy's Merlin helicopters and by adding operational flexibility through extra storage capacity and accommodation. They are very welcome."

The Prospect union voiced its "deep concern" over the loss of so many skilled shipbuilding jobs and has called for an urgent meeting with ministers and the company.

Deputy general secretary Garry Graham said: "For an island nation and in this time of increased global uncertainty, we should be seeking to maintain our shipbuilding capacity, not reduce it.

"Shipbuilding is not only a key element of our defence infrastructure, it is also an industry where the UK should be a world-leader, creating and sustaining highly skilled and well-paid jobs.

"Job losses of this scale will have a devastating impact upon local communities and economies. These are the very type of highly skilled jobs which should be leading us out of recession and helping create growth in the economy."

Conservative MP Mark Hoban, whose Fareham constituency neighbours Portsmouth, warned that the area would need Government support to deal with the blow.

The ex-minister, who lost his frontbench position in David Cameron's recent reshuffle, said it was "a very sad day for all those who work in Portsmouth shipyard".

"End of era for naval ship building on South Coast. Need Govt. help for area," he wrote on Twitter.

There was no immediate comment from Portsmouth North MP Penny Mordaunt, who was recently appointed as a Commons aide to the Defence Secretary.

But the move was attacked as a politically-motivated "act of lunacy" by one of the city's Conservative councillors.

Alistair Thompson said: "This is devastating for the workers and their families but also for all those people involved in the supply chain that keeps the dockyard working.

"Many of those who I represent as a councillor are hugely concerned that this decision has been taken for political reasons because of the referendum in Scotland next year.

"It makes no sense to close England's most advanced ship-building facilities. It is an act of lunacy that could make us reliant on foreign shipyards for the supplying of the Royal Navy.

"The other point is that this causes irreparable damage not only to the country's ability to build new ships but also maintain them. The jobs that are being lost are highly skilled and once they are gone it will take years to build them back up.

"This is something that the Government should realise. It is certainly something BAE know as they encountered this problem when shipbuilding moved back to the city only a few years ago."

Jamie Webster, convener of the Confederation of Shipbuilding and Engineering Unions at the Govan yard in Glasgow, said: "Obviously it's not a good day for the Clyde and for colleagues in Portsmouth. It's a disastrous day and my heart goes out to them. We're just workers, the same as them.

"We are going to have further detailed discussions with the company next week in England and we've told the workforce that and asked them to be patient with us.

"It's not the first time we've faced adversity but we'll come through this bruised but not beaten.

"We'll know the full picture on Wednesday and I'm absolutely confident Clyde will come out of this with the best result we can possibly get.

"We're in for a difficult two years but we won't be doing a runner. We didn't fight for a decade to get youngsters a job to just throw that in now."

He added: "I believe Clyde is going to suffer something like 800 job losses. We're not goners and we will work for the best result possible. You have to understand Govan and Scotstoun are one workforce together. We're only across the river.

"We've come through adversity before and I'm saying it again: we didn't spend 10 years bringing kids into this industry to watch them get put out the door. That will not happen."

Workers at the Govan yard were called to a meeting with management at 11am and began filing out 10 minutes later, having been told to go home.

At Prime Minister's questions Mr Cameron said: "These are extremely difficult decisions and our first thoughts should be with all of those that are affected."

He added: "We want our Royal Navy to have the best and most modern ships and the best technology. That means we will go on building warships on the Clyde, we will be announcing three new offshore patrol vessels, keeping that yard busy rather than paying for it to remain idle as the last government proposed.

"In Portsmouth, yes there will be job reductions, but there are many more people involved in ship servicing than in ship building, so the workforce will go from 12,000 to 11,000."

In his response to the SNP's Westminster leader Angus Robertson he added: "N o one should be in any doubt of two things: under this Government we will have aircraft carriers, Type 45 destroyers, the new frigates, the hunter-killer submarines.

"And there's something else they should know: if there was an independent Scotland we wouldn't have any warships at all."

Scotland Secretary Alistair Carmichael said that despite news of the shipyard closures, the Government was working hard to promote business in Scotland.

Asked for assurances from Labour's Margaret Curran that the legacy of the Commonwealth Games in Glasgow would not go to waste following today's news, he said: "I give you every assurance that, as was the case recently in the crisis surrounding the Grangemouth petrochemical plant, I will work with any party in any part of the country where Scotland's vital interests are concerned.

"I extend that invitation to you, to the Scottish National Party, to the Scottish government."

Although he acknowledged the significance of BAE's announcement, he said: "It was a day we always knew was coming. But working together we will manage to meet the challenges much more effectively."

Ms Curran had said: "The legacy of the Commonwealth Games is vitally important for the people of Glasgow and its future prospects, particularly in relation to jobs in Glasgow.

"But this has today been overshadowed by reports concerning the future of shipbuilding on the Clyde. The workforce on the Clyde is renowned for its skills and expertise, and today they face uncertainty about their future.

"Can I ask you to assure the House that you will work with trade unions and the company to minimise any potential job losses, mitigate the effects on community and secure the future of shipbuilding on the Clyde?"

SNP MP Angus Robertson said it was a "sad day" for Scottish families.

"Today is a very sad day for many families in Glasgow, and I'm sure the thoughts of everybody on all sides of the House is with them.

"How will the legacy to Glasgow of the Commonwealth Games be affected by large-scale industrial job losses in the city?"

Mr Carmichael replied: "As I have already said, we are working with the UKTI in order to bring more business opportunities to Glasgow. As far as the announcements are concerned, we will hear from the Secretary of State (for Defence) later today what the full extent of these are going to be.

"But these will be best tackled if we all work together. We have known for a long time that this day was coming."

He added that BAE Systems had "in very difficult circumstances, handled themselves in a way which is to be commended".