Union leaders have called for “cast-iron guarantees” over the future of workers at the business after Kraft Foods succeeded with its takeover of Cadbury.

Kraft’s cash-and-shares deal, recommended by the Cadbury board two weeks ago, values the Birmingham firm at around £11.4 billion.

The result came as hundreds of Cadbury workers staged a noisy protest in Westminster to call for guarantees for their jobs and conditions.

Speaking after the US giant secured 71.7 per cent of Cadbury shareholders’ votes, Jack Dromey, deputy general secretary of Unite, said: “This is a sad day for Britain. A world class sector of British excellence is “being taken over by a debt-laden US company.

“We now want cast iron guarantees from Kraft about the future for workers, and we want the Government to act as guarantor.”

Workers at the central London demo chanted Keep Our Jobs, and held up banners which read Don’t Sell Us Out. One protester was dressed in a gorilla outfit, banging a drum, to copy a Cadbury’s TV advert.

Mr Dromey added: “This must never happen again - the law must change to prevent hostile takeovers of successful British companies. We need a Cadbury law. We want Kraft to sit down with the unions, tomorrow, to discuss the future.”

Deborah Matthews-Booth, who has worked at the Bournville plant in Birmingham for 33 years, wore her factory uniform as she joined the protest to voice her concern about jobs.

“This is a very sad day for the workers - we have been left in the dark about the future. It is like a bereavement. All the workers, from the office staff to the production workers, are worried about their jobs.

“The Government should have done more to stop this happening - they could have stepped in to help us.”

Rob Phillips, who has worked at Cadbury’s factory in Leominster for 27 years, said: “We are really disappointed at the way this has turned out. Cadbury’s has been a good employer but there are real worries now about what will happen under new ownership.

“There will be no British manufacturing left soon. The Government had a big opportunity to do something but they didn’t. They have let us down. This would never have happened in France or Germany.”

Business Secretary Lord Mandelson will be meeting Kraft management, including chief executive Ms Rosenfeld, tonight to discuss the company’s plans for Cadbury.

“We understand the strength of feeling for this company across the UK, however the decision on the Kraft bid is a matter for the Cadbury shareholders,” said an official at the Business Department.