Drug maker Pfizer is to close its research and development (R&D) facility in Kent, which employs 2,400 people.
The move has raised concerns that the UK is losing highly-skilled jobs and about the private sector's ability to absorb cuts in the public sector.
The Unite union said the roles were "exactly the sort of jobs we need to keep in this country".
Business Secretary Vince Cable said the firm's decision was not about the UK as a location for pharmaceutical research.
Pfizer said the majority of staff would be made redundant over the next two years.
But it hopes to transfer several hundred positions to other sites or other companies doing work for Pfizer.
"This closure exposes the government's vacuous claim that the private sector will compensate for its brutal cuts," Unite's national officer, Linda McCulloch said.
Colin Blakemore, professor of neuroscience at Oxford University, called it a "shocking wake-up call".
"We must respond to this signal that one of our most important industries no longer has confidence in the future of British science."
Business Secretary Vince Cable called the decision "extremely disappointing".
But he added: "The company has been clear that this decision was part of its global programme of change and not based on a judgement of the UK as a location for pharmaceutical research."
Mr Cable said he would be meeting Pfizer, other companies and local representatives "as a matter of urgency to discuss innovative ideas for continuing R&D activities in this very well-equipped facility".
Labour's shadow business secretary called it a "deeply worrying development".
"Pharmaceuticals must be a sector where Britain's world reputation secures jobs and growth for the future," said John Denham.
"This Conservative-led government has no plan for jobs or growth; we cannot afford to lose global industries as easily as this."
The government has stressed the importance of innovation, skills and new technology to the UK's economic recovery.
Prime Minister David Cameron reiterated that the government was keen to diversify the economy when he announced an agreement with IT giant Cisco this week, that is expected to create new high-skilled jobs in East London.
The closure of the Kent facility is part of Pfizer's reorganisation of its research and development across the world.
The Sandwich site develops drugs for a range of disorders such as allergies and infectious diseases including HIV.
Pfizer's Ruth McKernan, who heads the site, said it had played "an important role in the discovery and development of medicines and has brought many life-saving treatments to patients".
A company spokesperson confirmed the decision to close Sandwich did not reflect any unhappiness with government policy.
Pfizer said that although it was moving out of the Sandwich site it hoped that R&D would continue there with a "partner organisation".
Conservative MP for South Thanet, Laura Sandys, said it was a "body blow" for east Kent and a "big shock to the community".
Pfizer closed its manufacturing operations in Sandwich in 2007.