Downing Street views the Cabinet Office as an extension of Number 10, according to former minister Mo Mowlam.

This attitude led to greater intervention in its day-to-day running by Number 10, she told the Press Association. "That made it very difficult."

Mowlam accepted the role of Cabinet Office minister in a reshuffle which saw her depart from the Northern Ireland Office after turning down the job of health secretary and the official Labour candidacy for London mayor.

Mowlam felt she had to be "vaguely reasonable" about changing departments.

But she criticised the Cabinet Office role now held by John Prescott, who also holds the position of deputy prime minister.

"It is not a big job and it's a very difficult department to manage because it's so diverse. It's not a real job in that sense and it got worse as time went on," she claimed.

The former MP for Redcar also says that her successor, Peter Mandelson, only talked to those people that were of use to him.

"I think that is Peter's downfall. His failure is that when you are of no more direct use to him, to ignore you. That aggravates people," she said.

"It's always Peter, Peter, Peter, without seeing the full picture in a rounded sense. So I don't think he necessarily did a good job."

In the interview, she also repeated claims of the damaging rift between Tony Blair and chancellor Gordon Brown.

"You accepted they didn't get on well. You could tell from the body language, you could tell from the lack of communication between them in cabinet, that they weren't close," she claimed.

However, Mowlam denied that she was left bitter by her ministerial experience.

She said: "In politics, if you took every bit personally you would never survive."