The Labour deputy leader says his decision was not down to "personal attacks and security threats" he has received over the last 12 months, but because he does not want to "spend every waking hour on conference calls and away from my loved ones".
Shadow culture secretary Mr Watson, who had served as the MP for West Bromwich East since 200, announced his decision last night just hours before his former Labour colleague and Dudley North MP Ian Austin also revealed he is standing down.
Mr Watson had repeatedly clashed with Jeremy Corbyn over anti-Semitism and the party's stance on Brexit, and survived a Momentum-led bid to oust him at the Labour conference in September.
Unlike Mr Austin, who says he will support the Conservatives at this election to stop Mr Corbyn, Mr Watson said in a letter to the Labour leader that his decision to stand down was "personal not political", adding that he will continue to devote himself to issues including gambling reform, music and arts, press intrusion, obesity and public health.
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 response Mr Corbyn thanked Mr Watson for his service, adding: "This is not the end of our work together."
Mr Watson said it had been his "immense honour" to represent people from Sandwell, adding that it was "hard to find words" to express his gratitude to the people who "trusted me to fight their corner".
"The Black Country is the very best of Britain. Communities who look out for their neighbours, who want to get on but not at the expense of others. Black Country people are the best in the world," he said.
"But now is the right time for me to stand down from national politics. The disagreements we have had inside the party are well-known; now is not the time to rehearse them again."
Thank you @tom_watson for your service to our party and your constituents. I know you’ll continue to take on the vested interests of the Murdoch empire, big sugar companies and the gambling industry. This is not the end of our work together. pic.twitter.com/MpYLVklHdr— Jeremy Corbyn (@jeremycorbyn) November 6, 2019
He said he wants to devote the next phase of his life to public health, using his experience and working with entrepreneurs and public servants, and setting up a "remission for all" movement for type 2 diabetics.
"I am incredibly optimistic about reversing the national public health crisis through education, deep technology and public policy," he added.
Mr Watson has been one of the most vocal members of the shadow cabinet calling for a second referendum.
I had my differences with Tom Watson or I wouldn’t have been standing against him. But I was once a supporter of his and even briefly a friend. I am from the same trade union and labour movement as him and it seems to me only right that tonight I wish him well in his life. pic.twitter.com/PXwbGIBVNJ— George Galloway (@georgegalloway) November 6, 2019
Mr Watson said he plans to campaign "across the country" to get Labour elected on December 12.
The deadline for candidates to announce they are standing in the election is November 14, giving Labour one week to find a replacement in West Bromwich East.
Here's Mr Watson's statement in full:
"Serving the Labour Party has been the privilege of a lifetime. I joined in 1982 and never imagined that one day a kid from Kidderminster would be the party’s deputy leader.
"Most importantly for me, for the last 18 years it’s been my immense honour to represent people from Sandwell. It’s hard to find words to express my deep gratitude to the people who trusted me to fight their corner.
"The Black Country is the very best of Britain. Communities who look out for their neighbours, who want to get on but not at the expense of others. Black Country people are the best in the world.
"But now is the right time for me to stand down from national politics. The disagreements we have had inside the party are well-known; now is not the time to rehearse them again.
"For me, the last few years have been personally transformational, second only to becoming a proud father of two beautiful children.
"Downsizing and becoming healthy for the first time has inspired me to devote the next phase of my life to public health, using my own experience and working with entrepreneurs and public servants.
"I am incredibly optimistic about reversing the national public health crisis through education, deep technology and public policy.
"I will devote myself to writing about this challenge, agitating for policy change and setting up a ‘remission for all’ movement for type 2 diabetics. I will announce further plans in the coming months, but I am excited about working with people I’ve met and many I’ve not.
"I might be leaving Westminster but I won’t be leaving politics altogether.
"I will continue to champion progressive social democracy and a political culture that is inclusive, diverse and respects the opinions of others. In recent years we’ve lost sight of that simple politeness which used to define us as a nation. We need to find it again.
"I will not be walking away from the election campaign. I will continue as Deputy Leader until December 12th and will do everything I can to return a team of bright, progressive Labour MPs.
"Since its formation, the Labour Party has been the most powerful vehicle for social change this country has ever produced. I am deeply proud of what past Labour governments achieved and determined that we do so again."