WARRINGTON South MP Helen Southworth is to stand down at the next general election.
The Labour backbencher says she wants to spend more time with her family, having represented the constituency since her election in the 1997 landslide.
The 52-year-old said the decision had not been an easy one but followed a great deal of thought over the last year.
She added representing the area had been a "tremendous privilege" but it was time to move on.
Over the next few weeks, the constituency Labour party will begin the process of finding a new candidate.
In 2008, Ms Southworth’s work with vulnerable children was recognised by the Missing People charity with the title MP of the Year.
Cllr Steve Wright, chairman of Warrington South Constituency Labour Party, praised the work she had done for the area.
She said she hoped to focus on the areas she has specialised in in Parliament by working with organisations that helped vulnerable young people, adding: "I also really value the personal support and friendship I have received from so many people in Warrington."