Here BBC News Online remembers those who have come - and gone - before.

July 1998: Social Security Minister Frank Field resigns after Tony Blair decided not to give him the job of his boss, Harriet Harman, when she was dropped from the cabinet.

October 1998: Welsh Secretary Ron Davies becomes the first cabinet minister to quit after the "moment of madness" which saw him robbed by a male stranger on Clapham Common.

December 1998: Trade Secretary Peter Mandelson resigns for the first time, as does Paymaster-General Geoffrey Robinson, the man who secretly gave him a �373,000 home loan.

October 1999: Jack Cunningham resigns as cabinet "enforcer" after constant predictions of his departure.

January 2001: Peter Mandelson resigns again, this time as Northern Ireland Secretary after claims he had helped the Hinduja brothers, Labour donors, in their efforts to get British passports.

Mr Mandelson was later cleared by the Hammond inquiry of "improper" behaviour.

May 2002: Transport Secretary Stephen Byers resigns after months of calls for him to be sacked.

The pressure began when his special adviser, Jo Moore, sent an email suggesting 11 September was a "good day to bury bad news".

Later, he was accused of misleading MPs over his decision to put Railtrack into administration and over the resignation of his media director, Martin Sixsmith.

Mr Byers denied lying but said he decided to go because he had become a distraction for the government and the Labour Party.