Sajid Javid has announced he will not stand in the next general election, saying being an MP had been "the privilege of [his] life".
The former chancellor, who has held a number of senior roles in government alongside his Bromsgrove seat, is the most high-profile Tory MP to decide to step down at the next national vote, expected in 2024.
It comes amid reports the Conservative Party has told its MPs to decide about their future by Monday, with a number of younger members already confirming their exits.
He has also made the announcement on the day Labour secured an historic majority in the City of Chester by-election, with stark warnings that such a swing nationally could cause the Tories big problems the next time the country goes to the polls.
In a letter to his party chairman posted on Twitter, Mr Javid said it was "a decision I have wrestled with for some time", but one that had been "accelerated" due to the party deadline.
"Being the local MP and serving in government has been the privilege of my life and I am immensely grateful for the opportunity to serve," he said.
"I always sought to make decisions in the national interest, and in line with my values, and I can only hope my best was sufficient."
He pledged the decision would not impact his work as an MP during his remaining time in office, adding: "I will of course continue to support my friend the prime minister and the people of Bromsgrove in any way I can."
'Proud champion of enterprise and opportunity'
Prime Minister Rishi Sunak said he was "sad to see my good friend... stepping back from politics", tweeting: "He's been a proud champion of enterprise and opportunity during his time in government and on the backbenches - particularly for the people of Bromsgrove."
Ending with a Star Wars quote, the PM added: "May the Force be with you, Saj."
Mr Javid first came into parliament in 2010 at the start of the coalition government, and got his first job on the front bench in 2012 as economic secretary to the Treasury.
Over the past 12 years he has held some of the highest offices of state, including home secretary and chancellor.
Mr Javid quit the latter role in 2020 - less than three months into the job - after the then-prime minister Boris Johnson and his senior adviser Dominic Cummings insisted he sack his aides and replace them with ones chosen by Downing Street.
He returned to Mr Johnson's top team as health secretary in June 2021 after Matt Hancock resigned after being caught on CCTV kissing one of his aides and breaking his own COVID guidance.
But he was the first minister to resign in the wave of exits that led to Mr Johnson's downfall over the summer, followed minutes later by then-chancellor and now prime minister Mr Sunak.
Mr Javid twice ran for the leadership of his party, but lost out to Mr Johnson and his successor, Liz Truss.