Lord Mandelson said he was “disappointed” after Cadbury’s new US owner was unable to confirm the chocolate maker’s brands would still be run from the UK.
The Business Secretary met Kraft chairman Irene Rosenfeld a few hours after the US food giant won its battle for control of Cadbury.
Lord Mandelson said: “I was disappointed that she was unable to confirm that Cadbury’s confectionery brands will continue to be managed and operated globally out of the UK.
“On the other hand she said that she expects Britain to be a net gainer in manufacturing output and employment so that was encouraging, but what we’ve got to do now is to remain in close touch.”
He added: “I’m glad now to be in personal touch but what I will be looking for are much harder, more specific commitments in the next three to six months.”
Kraft’s successful battle for Cadbury shareholder approval heralds the end of the iconic British firm’s 186-year history as an independent company.
It employs around 6,000 people in the UK, at sites including Cadbury’s Bournville site in Birmingham and Somerdale, near Bristol.
Speaking after the meeting, Ms Rosenfeld said the deal would be good for British manufacturing jobs but would not give any cast-iron guarantees about staffing.
“As we have said from the outset, our interest is in growing Cadbury and investing in its great brands and people,” she said.
“That will be good for the company, good for the UK and good for British manufacturing jobs.”
Ms Rosenfeld added: “We aim to restore Cadbury to its place as the world’s biggest and best confectionery business.
“Lord Mandelson was naturally interested in the employment prospects of Cadbury’s workers.
“I made clear to him our belief that the combination of Kraft Foods and Cadbury will be better for UK manufacturing than Cadbury’s standalone prospects.”
Investors holding 71.7 per cent of Cadbury’s shares backed the Kraft takeover.
When the US giant passes the 75 per cent threshold it will take the company off the stock market, and when it reaches 90 per cent support it can automatically buy up the remaining shares.
The cash-and-shares deal, recommended by the Cadbury board two weeks ago after a five-month negotiation, values the UK firm at around £11.4 billion.
Earlier hundreds of Cadbury workers staged a noisy protest in Westminster to call for guarantees for their jobs and conditions.
They pressed for a new law to be introduced to prevent any more British “icons” being bought up by a foreign firm.
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.
She said: “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.”
Felicity Loudon, a member of the Cadbury family, also said it was a “sad day for Cadbury and for Britain”.
“There was always a certain inevitability about this acquisition but that doesn’t make Kraft any more palatable to me or most of the population of the UK,” she said.
She also attacked the “dismal” performance of the Cadbury board and accused chief executive Todd Stitzer of “quietly grooming Cadbury for a sale for some time”.
Ms Loudon added: “It only remains for me to call upon Kraft to honour their pledge to keep chocolate production alive in England and to respect the traditions of the proud British institution they now control.”
A Cadbury spokesman said: “Cadbury may now be part of Kraft Foods but, as far as employees here and the public at large are concerned, it will be very much business as usual when we all wake up tomorrow.
“Cadbury chocolate isn’t going to change and the Cadbury brands that we all know and love won’t disappear either. Kraft Foods has made it very clear they bought the company precisely because our chocolate is so popular and they have committed to building on both our brands and heritage here in the UK.”