The scathing comments come as the former foreign secretary returned from his holiday in Italy amid an escalating row within Conservative ranks over his suggestion that women wearing the religious headgear resembled “letterboxes” and “bank robbers”.
Reports on Sunday claimed four cabinet ministers had privately expressed dismay at the party’s handling of the case after it was decided Mr Johnson should face a disciplinary investigation.
“It’s been so cack-handed. Boris is a backbencher. What he said wasn’t that outrageous; a lot of people have said worse and a lot of the party happens to agree with him,” one minister told the Sunday Times.
“The sooner the party throws this investigation out, the better. Lots of people both on the front and backbenches are really p***** off.”
Mr Johnson made no comments on the furore as he arrived at his Oxfordshire home on Saturday evening but he is expected to break his silence in his regular Monday column for the Daily Telegraph, where his comments about the niqab were printed six days ago.
Addressing the row, Lord Cooper, a Conservative peer and former director of strategy for 10 Downing Street, said: “The rottenness of Boris Johnson goes deeper even than his causal racism and his equally casual courting of fascism.
“He will advocate literally anything to play to the crowd of the moment. His career is a saga of moral emptiness and lies; pathetic; weak and needy; the opposite of strong.”
On Sunday, however, a survey found that 53 per cent were opposed to punishment for Mr Johnson while 40 per cent said he deserved to be disciplined for his comments about the niqab.
Mr Johnson’s father, Stanley, rallied to the defence of his son on Sunday in an article for the Daily Telegraph, saying he would have liked him to “go further”.
“Yes, Boris used some colourful language. That's called 'freedom of speech' or it was in my day,” he wrote.
He continued: “But he said what needed to be said. As a matter of fact, I would have liked him to have gone a bit further. He was against 'banning the burka'. But surely, there are circumstances where a ban or appropriate restrictions would be in order.”
Far-right US activist Steve Bannon, who was in contact with Mr Johnson during his recent visit to the UK, also urged him not to "bow at the altar of political correctness" by apologising.
The former aide to Donald Trump told the Sunday Times that Mr Johnson had "nothing to apologise for."
But former first secretary of state Damian Green, who was Ms May's de facto deputy, said he feared Mr Johnson was "being turned into a martyr by the alt-right", which would be "a disaster for him and the Conservative Party".
Writing for the Mail on Sunday, he said: "I am particularly concerned by reports that President Trump's sacked adviser Steve Bannon is forming a Europe-wide far-right campaign group - and has been in touch with Boris.
"I hope that no Conservative politician, including Boris, is taking advice from him about how the Conservative Party should behave."
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