BORIS Johnson had no reason to block the appointment of Chris Pincher as Tory deputy chief whip, Downing Street has said, despite appearing to acknowledge there had been concerns about him.

Pincher dramatically quit on Thursday after a drunken incident in which he allegedly groped two male guests at a London private members’ club.

The Prime Minister was under pressure to go further and suspend him from the Tory Party, while opposition parties said his position as an MP was untenable.

Downing Street appeared to acknowledge that there had been concerns when he was appointed to the key post of deputy chief whip, with responsibility for discipline over Tory MPs, in February.

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However a No 10 spokesperson said the Prime Minister had not been made aware of anything that would have prevented the appointment going ahead.

“In the absence of any formal complaints, it was not appropriate to stop an appointment on the basis of unsubstantiated allegations,” the spokesman said.

Meanwhile, the only two women Tory MPs to chair Commons select committees – Caroline Nokes and Karen Bradley – have called for a policy of “zero tolerance” for any such alleged conduct, with any MP facing such allegations having the Conservative whip withdrawn while they are investigated.

In a joint letter to the Prime Minister, they said: “The party and, by extension, the Government are at risk of serious reputational damage by the current approach.

“We urge you to act swiftly to introduce a code of conduct for all Conservative members of Parliament which is clear in terms of the expectations of behaviour and which can be applied in a fair, independent manner so as to avoid any suspicion of bias.”