Sussex's manufacturing industry was dealt a blow this week when drug giant GlaxoSmithKline axed more than 300 jobs in the county.

GSK said 180 workers were being made redundant at its manufacturing plant in Southdownview Way, in Worthing, and a further 130 jobs were being shed at its factory on the Manor Royal industrial estate in Crawley.

The multinational company, which made £1.9 billion in the three months to September, said it wanted to cut costs by £700 million over the next three years to offset falling sales of diabetes treatment Avandia. The drug has been linked to an increased risk of heart attack.

GSK said the job losses in Sussex would take effect between April next year and the end of 2009 and were likely to include some compulsory redundancies.

Unions reacted with fury to the announcement.

Linda McCulloch, Unite national officer for the Pharmaceutical industry, said the job cuts at GSK were being made "solely to keep shareholders happy".

She said: "This is a profitable company that does not need to cut jobs or make closures and we will fight any attempt by the company to do either."

Alistair Smith, chief executive of the West Sussex Economic Partnership, added: "We are very disappointed by this news and commiserate with those people who are losing their jobs, and we would hope some would be voluntary redundancies.

"It is good news that they are keeping the factories open. That would suggest they still think there will be opportunities here in the future, one would hope."

He added: "There are, of course, plenty of good job opportunities in West Sussex and we will be working with Seeda (the regional development agency) and other partners to help any staff who become redundant to find new openings in the local area quickly."

The Worthing site will continue to employ about 900 people after the redundancies, while 520 workers are being kept on at Crawley.

Crawley site director Ian Holdstock said the job cuts were in response to reduced demand for key products and a need to improve efficiency and productivity at the site. He said: "We regret the impact of this proposal, but would like to emphasise that today's announcement is based on a review of the forecast volumes and the need to improve the efficiency of our operations.

This is not a reflection of the performance of our employees. The site has a good customer service record and has contributed to a number of successful product launches this year. This is disappointing news but we are committed to supporting our staff though these difficult times."

The company said it was entering a period of consultation with staff at both sites. GSK, which employs almost 100,000 people worldwide announced a seven per cent drop in pre-tax profits to £1.88 billion for the three months to the end of September.

Sales of Avandia plummeted by 38 per cent in the quarter to £225 million with demand for the treatment hit more than expected.

The drug was a one-time bestseller for GSK, but has seen sales tumble since evidence earlier this year linked the drug to an increased risk of heart attack.