Prime Minister Gordon Brown has warned the UK may have to make massive reductions in carbon emissions - or face the sea sweeping away swathes of Sussex.

Mr Brown, speaking in the Commons yesterdayFEB20, said the Government would have to be "far more radical" when it came to setting legally binding targets to tackle climate change.

Under current estimates, without effective action to curb emissions, Britain's sea level is expected to rise by up to 69cm on 20th century levels by the 2080s.

Dr Alister Scott of the Sussex Energy Group, one of the world's largest independent research groups into energy and climate change, said a mixture of rising sea levels and stormy weather could place coastal defences under threat in places such as Brighton and Hove, Seaford, Eastbourne and Hastings, as well as the low-lying Cuckmere Valley.

He said: "With sea level rises at that level we would be pushing the boundaries of what the defences as they are currently built could handle, making a breach more likely. As things currently stand we are a long way from doing enough on climate change."

The Climate Change Bill, currently going though Parliament, will commit the Government to cutting carbon emissions by at least 60 per cent by 2050.

But Mr Brown told Prime Minister's Questions an independent climate change committee had been asked to consider whether ministers should go for a more ambitious 80 per cent reduction instead.

Mr Brown was responding to Hove MP Celia Barlow, who said all "sane" people now believed climate change was going to create a "challenging world".

Ms Barlow, a Labour MP, said more than 600 of her constituents had written begging her and other MPs to be "brave and bold by setting more ambitious targets".

She asked the Prime Minister: "Will you assure my constituents that our Government will continue to take the lead in tackling climate change by agreeing to more challenging targets, lest the seas swell and sweep away Hove and Portslade?"

Mr Brown replied: "I do agree with her that we may have to be far more radical in the targets we set for cutting carbon emissions.

"We have set a target of 60 per cent by 2050. We have now set up the new climate change committee. We will ask it to look at a new target of 80 per cent, which is a far bigger target of carbon emissions than before."

He added: "We are the first country in the world to have legislation that legally requires the Government to ensure that carbon emissions are cut every decade and in particular we will take action in the next few years to get a new world climate change agreement."

Lewes MP Norman Baker said the Government's failure to cut the costs of public transport threatened to hinder its progress on reducing emissions.

The Liberal Democrat transport spokesman told Mr Brown: "According to official Government figures, since 1997 the real cost of travelling by train has gone up six per cent above inflation, the cost of going by bus up 13 per cent and the cost of going by car down ten per cent.

"Why do you want to penalise the public transport user, and how does that help your climate change objectives?"

Mr Brown said Labour had doubled investment in the railways and guaranteed free national concessionary bus travel for all pensioners.

Don't miss Going Green with our award-winning environment co-ordinator Sarah Lewis in Saturday's Weekend supplement.