Staff at GlaxoSmithKline's Brentford headquarters face an uncertain future after the company announced it would be axing jobs as part of a £1bn cost-cutting drive.

The firm did not reveal how many jobs would be cut from its 100,000-strong global workforce or the impact on UK staff.

But it said it was looking to increase annual cost reductions from £700m to £1.7bn by 2011.

Glaxo has a number of UK sites, including the global headquarters in Brentford, Middlesex, and manufacturing operations in locations including Kent, Cumbria and Ayrshire.

The drugs maker has already cut 2,000 positions in the UK out of 10,000 roles axed globally since 2007, when it first announced a programme to cut costs.

Last autumn it announced the closure of its huge plant at Dartford in Kent where 820 staff are based.

Glaxo declined to confirm if further sites will be shut in the latest round of cost reductions, but said the majority of cuts would not be in the UK.

Glaxo said: "We are very conscious of the effect this programme will inevitably have on our employees and if options exist where we can achieve our financial goals and preserve jobs, we will do everything we can to do so.

"Where no other option aside from redundancy exists, we will support those employees affected in every way we can."