Sir Tony Cunningham, who was knighted two years ago, has represented the constituency since 2001.
The 61-year-old said he felt it was the right time to go and he planned to spent more time with his family.
Labour held the seat with a 4,575 majority in the last election and it will now begin a selection process for a candidate to defend it in May 2015.
Locally-born Sir Tony was a teacher, local councillor, then mayor of Workington and became an MEP in 1994.
Fellow Cumbrian MP Tim Farron, who holds the Westmorland and Lonsdale seat for the Liberal Democrats, tweeted: "Sorry to hear that Tony Cunningham has decided to stand down at the next election.
"He was a great MP & a kind, thoughtful and decent man."
The Labour MP for Workington has announced he will stand down at the next general election.