More than 1500 jobs could go in Sussex because of falling sales at drugs giant GlaxoSmithKline (GSK).

The multinational is trying to slash costs by £700m over the next three years because of dropping revenues.

Bosses at GSK, which employs 900 people in Worthing and 650 in Crawley, say they will need to axe jobs if they are to meet their targets.

The company says it will not reveal the details of how many posts will go or where the jobs will be shed yet.

A spokeswoman said: "We want to speak to our employees first. Once we have done that and the review is complete we will be able to give more details."

But tonight local leaders were promising to fight job cuts in Sussex.

Bob Lanzer, the leader of Crawley Borough Council, said: "The council is committed to maintaining a vibrant economy in Crawley and we work very closely with business.

"This is very concerning news but at this point we don't know if any sites are at risk and we would seek to establish that.

"With 650 jobs provided in Crawley it would be a significant blow if the site was closed and we would want to use our influence best as we could to avoid job losses."

The global drugs company, which also has factories in Dartford and Maidenhead, is trying to cut costs to offset falling sales of diabetes treatment Avandia which was linked to a health scare earlier this year.

Less than three months ago rival pharmaceutical giant AstraZeneca announced a similar three-year cost cutting plan, which would see the loss of 7,600 jobs.

GSK, which employs almost 100,000 people worldwide, said it would have to shut down "a number of manufacturing sites" under its savings strategy.

The group said its manufacturing division and the group's selling and administration arm will be hardest hit by the cost reduction plan.

The divisions will each contribute 40 per cent of the £700 million in savings, with the remaining 20 per cent to come from research and development.

GSK said it was considering offshoring and outsourcing some of its manufacturing capabilities.

News of the sweeping cost-saving plan comes as GSK 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 impacted more than expected.

The City was expecting a 28 per cent fall in Avandia sales over the quarter.

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

Jean-Paul Garnier, chief executive of GSK, said: "Sadly there will be some job losses and and possibly site closures, subject to consultation, and we'll do everything we can to support everybody involved in the process."

He added: "In some cases we'll be talking about adding jobs and expanding the business, but in terms of cuts, there will be cuts across the board."

GSK looks set for more problems surrounding its Avandia drug, with reports that the US Food and Drug Administration (FDA) might rule that the treatment has to carry heart-attack warnings. Avandia already carries a so-called black box warning about heart failure, but a heart attack warning would be more serious.

GSK is expected to argue that there is no clear evidence linking Avandia to heart attack, but said today it was too early to comment until a final decision from the FDA.

Europe's regulators ruled last week that the benefits of Avandia - also known as rosiglitazone -continue to outweigh the risks, but recommended a tighter label.

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