An ally of Boris Johnson has resigned, triggering a third by-election for the Tories and creating deepening political problems for Rishi Sunak.
Nigel Adams did not say why he was leaving immediately but his decision follows that of Boris Johnson and, earlier on Friday, Nadine Dorries.
In a statement Mr Johnson lashed out at a Partygate report into whether he deliberately lied to Parliament, describing it as a "witch hunt".
Labour called him a "coward".
Mr Adams, a Cabinet Office minister without portfolio under Mr Johnson's government, had previously announced he would not be standing at the next general election - but has now brought that decision forward.
In a tweet announcing he was going immediately, the MP for Selby and Ainsty said his local Conservative Association had selected a new parliamentary candidate on Friday.
By-elections sap energy, money and attention that the party would rather use to focus on governing and the general election.
The BBC has made dozens and dozens of phone calls and exchanged hundreds of WhatsApp messages since Boris Johnson made his shock resignation announcement on Friday evening.
It is clear there is deep - and wide - anger, if not surprise, at the way Mr Johnson and his allies have criticised the Commons Privileges Committee and the integrity of its members, who are duty bound to put party affiliation to one side, and not speak publicly about their report until it is published.
Announcing his resignation as MP for Uxbridge and South Ruislip late on Friday evening, Mr Johnson issued an eviscerating 1,000-word statement.
However, former home secretary Priti Patel, who was made a Dame in Mr Johnson's resignation honours list, also announced on Friday, praised the former prime minister, describing him as a "political titan".
Sir Michael Fabricant - another sitting MP announced in the resignation honours list - criticised the Privileges Committee for what he described as its "disgraceful treatment" of the former prime minister.
There has been no statement as yet from Prime Minister Rishi Sunak or any members of the Privileges Committee.
The BBC has tried to speak to all of those involved, but none would speak on the record.
But privately, Conservatives are all talking about it, trying to work out what might happen next.
Loads have told the BBC they are just totally fed up with the pantomime.
There is deep frustration there will now be three by-elections that the party could really do without.
The committee was preparing to recommend a 10-day suspension for Mr Johnson from the Commons, the BBC has been told, which would have resulted in a recall petition among his constituents and a potential by-election.
Mr Johnson said the draft report he had seen was "riddled with inaccuracies and reeks of prejudice".
He described the committee as a "kangaroo court" whose purpose "has been to find me guilty, regardless of the facts".
The committee is due to meet on Monday to finalise its conclusions and is expected to publish its findings shortly after - likely to be on Tuesday or Wednesday.
Angela Rayner, Labour's deputy leader, said the former prime minister had "jumped" and told BBC Radio 5 Live "to me, he is a coward".
Sir Chris Bryant, the Labour chairman of the Privileges Committee, said it was possible that Mr Johnson's statement could lead to further contempt of Parliament charges as the conclusion of the report is not supposed to be revealed before its publication and Mr Johnson had "effectively leaked" it.
Sir Chris, who had recused himself from the investigation into Mr Johnson told Radio 4's Today programme, the "attacks on the committee are in effect an attack on the whole House".
The surprise exit of Boris Johnson followed that of Nadine Dorries, who announced she was standing down as MP of Mid Bedfordshire shortly before.
The Conservatives have a current working majority of 64 (before the resignations of Mr Johnson and Ms Dorries).
This is less than the 80-seat majority held by the Conservatives when Mr Johnson led the Tories to a landslide general election in 2019.
Conservative backbencher Sir John Redwood said Rishi Sunak must make a statement "urgently reassuring those who were very strong Boris fans and strong Liz [Truss] fans that his party is for all Conservatives."
He told the BBC News channel the party will need "a bit of Boris magic" in their offer to voters.
But Tory grandee Chris Patten said he hoped Mr Johnson's resignation "is the end of a rather miserable period in British politics and a miserable period for the Conservative Party."
Lord Patten, who was party chairman under John Major, rejected claims the Privileges Committee's report was "anti-democratic".
"Of course it's not," he told the BBC. "What he means is it's criticised him... he should stop whining about it and get on with what he's plainly going to do best, which is going around making dishevelled speeches and making lots of money from them."