I told him [the prime minister] some time ago I would be leaving after the election

Margaret McDonagh

The newspaper group is owned by Richard Desmond who has made a fortune out of such titles as Asian Babes and Nude Readers Wives.

Ms McDonagh is not expected to have any involvement with those publications.

Ms McDonagh spent three years as Labour's general secretary before resigning after the election.

Although she was credited for her contribution to turning Labour into an efficient political machine, she drew flak over her role in one of the most embarrassing episodes in the party's recent history - the move to try to stop Ken Livingstone becoming mayor of London.

Mayoral fiasco

Ms McDonagh later apologised for the fiasco which saw Mr Livingstone defect to form a party of one when it became clear he was not going to be able to run as Labour's candidate.

He subsequently easily saw off a challenge from the official Labour candidate Frank Dobson.

Ms McDonagh explained her decision to leave her job as general secretary by saying that it was the "right time" for a change.

"I told him [the prime minister] some time ago I would be leaving after the election," she said.

"It's the right time for a change so that someone else can come in and start preparing for the next general election, which they will have to start thinking about quickly."

Ms McDonagh joined the Labour Party as a 17-year-old but it was in 1994, shortly after the death of John Smith that Tony Blair asked her to come and work on his campaign to become leader.

She was made general secretary in 1998.