The six candidates for the Tory leadership have been threatened with a "yellow card" in a bid by party chiefs to ensure the contest is a clean fight.
The shock move is aimed at preventing a repeat of the "constant backbiting" of the past five years, which Tory grandees blame for the party's crushing election defeat.
The threat suggests that the Tory high command is concerned that abuse of rivals during the campaign will project an image of a defeated party in a state of civil war.
The "yellow card" announcement came from 1922 Committee chairman Bob Blackman as he confirmed the six who will take part are those who have already declared.
Asked about a "red card", Mr Blackman said he hoped that would not be necessary, but insisted there would be sanctions if a candidate made a damaging statement about a rival.
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Battling to replace Rishi Sunak as party leader in three months' time will be Kemi Badenoch, James Cleverly, Robert Jenrick, Priti Patel, Mel Stride and Tom Tugendhat.
Speaking in hot sunshine outside parliament as nominations closed at 2.30pm, Mr Blackman issued a stern warning to the candidates that bitter personal attacks would not be tolerated.
Mr Blackman, who is returning officer for the election, will enforce discipline and hand out yellow cards if necessary, along with acting Tory chief whip Stuart Andrew and acting party chairman Richard Fuller.
"We are determined that this is going to be a good, clean contest between the candidates that have been nominated," Mr Blackman told political journalists.
"So you may have seen that we've got what's called a yellow card system in operation if candidates indulge in attacking each other."
Asked by Sky News how the yellow card system would work, Mr Blackman said: "The situation with the yellow card is very simple.
"The constant backbiting and attacking colleagues both in public and in the media in the last parliament was one of the reasons why the party did so badly in the general election.
"We are determined that we will not tolerate that happening. So if candidates indulge in it, then I will get involved, obviously, to warn them and if necessary, issue a public statement to the fact that they've been involved in such activity.
"If MPs get involved in such backbiting the chief whip will intervene. And if ex-MPs get involved, then the party chairman will get involved in making sure that suitable action is taken. And basically we just want to stop people from that constant backbiting."
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Tap hereAsked then by Sky News: "And what about a red card?" Mr Blackman, a football supporter who describes himself on X as an "avid Spurs fan", said he hoped that would not be necessary, but there would be sanctions.
He said that if a yellow card was issued, in response to a statement made to the public about a candidate that "infringed on the rules and would be extremely detrimental to their chances of getting elected, that should be enough".
He added: "And hopefully, hopefully we won't have to do it. But it's there as a sanction."
Mr Blackman also revealed the names of the proposer and seconder of the six candidates who received the backing of 10 MPs, ensuring they were validly nominated:
• Kemi Badenoch, proposed by Alex Burghart and seconded by Julia Lopez;
• James Cleverly, proposed by Gagan Mohindra and seconded by Peter Fortune;
• Robert Jenrick, proposed by Danny Kruger and seconded by Caroline Johnson;
• Priti Patel, proposed by Greg Smith and seconded Saqib Bhatti;
• Mel Stride, proposed by Jeremy Mayhew and seconded by David Reed;
• Tom Tugendhat, proposed by Karen Bradley and seconded by Neil Shastri-Hurst.
Mr Blackman added: "Those six candidates will now be free to campaign to appear in the media, to go to associations, to events all over the country as they wish. There's no requirement on associations to invite all of them. So it's up to them to do so."
Confirming the timetable for the election, he said: "There will be a ballot of MPs on Wednesday 4 September to reduce the number of candidates.
"If there are more than five candidates, there'll be a further ballot to reduce to four candidates, which will be the following week. And we expect to announce the final four, the week commencing 9 September.
"Those four candidates will go to the party conference and they'll be given a platform to speak at the party conference. There will be hustings and other events around the party conference.
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"When MPs return on 7 October we'll have hustings on 8 October, a ballot on 9 October and a further ballot, if necessary, on 10 October, to reduce the number of candidates to two.
"Then those two remaining candidates will go to the ballot of members. Ballot papers should be received around 15 October. The ballot will close on 31 October, with the announcement of the new leader on 2 November.
The new leader will take up post immediately, Mr Blackman added, and begin leading in parliament on Monday 4 November.
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