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 told the BBC: "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.
She said: "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."
