East of England Minister Barbara Follett has announced she will be standing down at the next general election.
The Stevenage MP said it was "with great sadness" that she told the Prime Minister and local Labour Party leaders she would not be contesting the seat again.
The 66-year-old mother of three said she wanted to spend more time with her family while she was "still fit and healthy enough to enjoy it".
She said in a statement: "No one in my very large and very dear family is getting any younger, least of all me. Over the summer my husband and children made it quite clear that, after 12 years, they had had enough of me being absent from important family occasions - or arriving late and leaving early...
"I am standing down to spend more time with my family. It is a cliche, but it is true."
Ms Follett is married to novelist Ken Follett.
She is Parliamentary Under Secretary for Local Government and has tried to reform the working hours at Westminster to make them less antisocial and more family-friendly.
She said: "If the hours of Parliament, which I have tried so hard to reform, had been anything approaching normal, my decision might have been different. But, despite improvements, Westminster's timetable remains very family-unfriendly."
The minister came under fire in May for the expenses she had claimed from the House of Commons Fees Office.
Receipts leaked to the Daily Telegraph showed she had claimed more than £25,000 for security patrols outside her London home between 2004 and 2008.
In June she announced she had decided to repay the sums she had claimed towards the security costs and also for the repair and cleaning of a child's rug which, she said, was claimed in error.
She offered Gordon Brown her full support, describing him as a "good and brave man."
She said: "I admire and respect the Prime Minister more than I can say."
Ms Follett joined the Labour Party more than 30 years ago and has been involved in politics since the age of 16.