Owen Paterson has announced his resignation as MP for North Shropshire, after Boris Johnson made clear he would no longer seek to prevent the former cabinet minister from being punished by parliament for lobbying.
Mr Paterson, who has been an MP for 24 years, was found by parliament's independent sleaze investigator to have broken lobbying rules during his £110,000-a-year private sector work, continued to maintain his innocence.
“I will remain a public servant but outside the cruel world of politics,” the MP for North Shropshire said in a statement.
Paterson was facing a 30-day suspension from the House of Commons and a potential by election, after Boris Johnson withdrew his support from an attempt to protect him.
On Wednesday, Conservative MPs - with the encouragement of the prime minister - passed a motion in favour of ignoring Mr Paterson's month-long Commons suspension.
As part of the backlash, the government was accused of "corruption" in seeking to overhaul parliamentary standards rules in an alleged effort to protect the MP.
Faced with a huge outcry, the government reneged on Thursday less than 15 hours later with the promise of a new vote on Mr Paterson's suspension.
But, just hours later, the 65-year-old announced his intention to resign from the House of Commons.
"I have today, after consultation with my family, and with much sadness decided to resign as the MP for North Shropshire," he said.
“The last two years have been an indescribable nightmare for my family and me. My integrity, which I hold very dear, has been repeatedly and publicly questioned,” Paterson said.
He said his children had asked him to leave politics, after what he claimed was the mocking and belittling of his wife’s suicide by “people including MPs”.
“I do not want my wife’s memory and reputation to become a political football. Above all, I always put my family first,” he added.
Responding to the resignation, the PM said in a statement that he could "understand why" Mr Paterson had "decided to put his family first".
"I am very sad that Parliament will lose the services of Owen Paterson who has been a friend and colleague of mine for decades," Mr Johnson said.
"He has had a distinguished career, serving in two cabinet positions, and above all he has been a voice for freedom - for free markets and free trade and free societies - and he was an early and powerful champion of Brexit.
"I know that this must have been a very difficult decision but I can understand why - after the tragic circumstances in which he lost his beloved wife Rose - he has decided to put his family first."
The Labour leader, Keir Starmer, responding to Paterson’s resignation, said: “This has been an unbelievable 24 hours even by this government’s chaotic standards.
“Boris Johnson must now apologise to the entire country for this grubby attempt to cover up for the misdemeanour of his friend. This isn’t the first time he’s done this but it must be the last. And Boris Johnson must explain how he intends to fix the immense harm he has done to confidence in the probity of him and his MPs.”
Mr Paterson was last month found by a Commons watchdog to have "repeatedly used his privileged position" to benefit Randox, a clinical diagnostics company, and Lynn's Country Foods, a meat processor and distributor.
He has continually declared himself "not guilty" and strongly criticised the investigation into his private sector work, which he said saw him raise serious issues about food contamination during his contact with officials.
Mr Paterson has also said the investigation "undoubtedly played a major role" in his wife, Rose Paterson, taking her own life in June last year.