Labour deputy leader Tom Watson has announced he is stepping down from the role and will not stand to be an MP in the General Election.
In a statement, the party said: "After 35 years in full-time politics, Tom Watson is stepping down as an MP and Labour's Deputy Leader.
"Labour Leader Jeremy Corbyn has thanked Tom for his contribution to the Party over three decades and paid tribute to the work he has done to take on the vested interests of the Murdoch empire, the big sugar companies and the gambling industry.
"Tom will continue to play an active part in the General Election campaign, as the country faces a stark choice: transformational change for the many with Labour, or more divisive austerity politics serving the few with the Tories.
"After the election, Tom will be focusing on campaigns to overcome the Tory-fuelled public health crisis. He will be setting up a new organisation championing remission for all type 2 diabetics and has a book on 'downsizing' coming out in January about his own health journey."
In a tweet, Mr Watson said: "After 35 years in full-time politics, I've decided to step down and will be campaigning to overcome the Tory-fuelled public health crisis. I'm as committed to Labour as ever. I will spend this election fighting for brilliant Labour candidates and a better future for our country."
After 35 years in full-time politics, I've decided to step down and will be campaigning to overcome the Tory-fuelled public health crisis. I'm as committed to Labour as ever. I will spend this election fighting for brilliant Labour candidates and a better future for our country. pic.twitter.com/qGqiKTJ6br
— Tom Watson (@tom_watson) November 6, 2019
In his letter to Jeremy Corbyn, Mr Watson said the decision had been "very difficult".
He added: "But now is the right time for me to stand down from the House of Commons and start a different kind of life. The decision is personal, not political.
"The last few years have been among the most transformational of my personal life, second only to becoming a proud father of two beautiful children. I've become healthy for the first time, and I intend to continue with this work in the years to come."
Mr Watson, who held the West Bromwich East seat since 2001, said he would still campaign for the party.
His letter continued: "I might be standing down as an MP but I won't be leaving politics altogether.
"This election is a turning point for our country and I know that Labour goes into it united in our determination to remove the Conservative government that has done so much damage to the communities Labour was founded to represent.
"I will be taking an active part in this election campaign. I will continue as Deputy Leader until 12 December and will do everything I can to return a team of Labour MPs who will transform our country."