Barbara Follett, the minister who claimed £25,000 on expenses for private security, is stepping down as an MP.
Miss Follett, a junior minister at the Communities department, will leave parliament at the next election.
She held her Stevenage seat in 2005 with a 3,000 majority, making it vulnerable to the Conservatives.
She said had made the decision for family reasons, saying she wanted to spend more time with her children and grand children.
The Daily Telegraph revealed earlier this year that Miss Follett claimed more than £25,000 over four years on parliamentary expenses for security patrols outside her home because she said she did not feel safe in London.
At the time, she said the claims were justified, but after facing public criticism of her use of allowances. She has since agreed to return a total of £32,976 for the security services and other questionable claims.