Three Labour MPs announced today that they would not be seeking re-relection.
David Chaytor said he would not be standing at the next general election, adding that his priority in the next few months would be to "explain my errors'' in relation to parliamentary expenses.
The former health secretary Patricia Hewitt also announced she was leaving Parliament at the next election, but denied her decision was related to the row over MPs' expenses.
And the Children's Minister Beverley Hughes announced she was stepping down as the MP for Stretford and Urmston.
Mr Chaytor has already been suspended from the Parliamentary Labour Party pending a "star chamber" inquiry into his claims.
Today he said he would not seek re-election for Bury North after discussions with colleagues, local party figures and senior Labour officials at the weekend.
He said that, for the coming months, his "priority must be to explain my errors following allegations over the use of parliamentary allowances".
"This will be time-consuming and stressful," he went on. "I have referred my case to the Parliamentary Commissioner for Standards and will co-operate fully with his inquiry."
Mr Chaytor, an MP since 1997, already faced being de-selected as a Labour candidate after it emerged he claimed almost £13,000 on a non-existent mortgage. He is to pay back the sum after continuing to submit £1,175 monthly bills for months after the loan was paid off.
In a statement this morning, he said he would continue his constituency and Parliamentary work "conscientiously and to the best of my ability".
He added: "I do not want my self-inflicted problems to be a distraction to my party's campaign as we move towards the General Election."
Mr Chaytor said MPs had failed collectively to reform an "archaic and secretive" allowances system.
Ms Hewitt, who is 60 and has been MP for Leicester West since 1997 and left the Government when Gordon Brown became Prime Minister in 2007, told the Leicester Mercury, that she wanted to spend more time with her family.
According to the Daily Telegraph, her claims included £920 in legal fees when she moved out of a flat in her constituency before staying in hotels and then renting another flat in Leicester.
She also claimed for furniture, including £194 for blinds delivered to her London home, the paper reported.
But Ms Hewitt said her decision was family-motivated, saying: "I did initially want to serve another term. But I feel the time is right.
"The truth is that after 13 years as an MP and 10 years in Government, I have not seen enough of my family. They have paid a high price for that."
Beverley Hughes announced she was stepping down for "personal reasons" and insisted her decision had "nothing whatsoever" to do with the expenses row.
According to the Daily Telegraph, Ms Hughes rented a second home in London where she claimed £801.60 for re-upholstering furniture, £718 on a chair and £435 on curtains and for bedding.
Children's Secretary Ed Balls praised Ms Hughes as "an outstanding minister for children and a champion of her region as minister for the North West".
Mr Balls added: "It's in no small part thanks to her drive and determination that this Government has been able to improve the lives of millions of children, young people and families in our country.