Rishi Sunak stands with Cabinet Secretary Simon Case, even though Downing Street does not deny that it failed to inform him of a written complaint about Dominic Raab.
The prime minister remains under pressure over what he knew about the intimidation allegations before appointing Raab as his deputy and attorney general.
Case is also facing scrutiny after the Times reported that the cabinet secretary was personally briefed on a complaint months before Sunak named his ally.
Number 10 did not deny the report suggesting that the cabinet secretary had been tipped off that public officials had made documented allegations about Mr Raab’s behaviour.
A Downing Street spokesman said the prime minister was not aware of any “formal complaints” before Raab returned to cabinet.
Asked if Mr Sunak is confident he is getting sound advice from Mr Case, the spokesman said: “Yes. The Prime Minister has full confidence in Simon Case.”
Case has also faced questions about his knowledge of Nadhim Zahawi’s tax affairs prior to his government appointments and his role in the controversy surrounding BBC Chairman Richard Sharp helping Boris Johnson obtain a loan. up to £800,000.
Deputy Labor leader Angela Rayner said: “No wonder Rishi Sunak refuses to say what he knew when he appointed Dominic Raab as his deputy.
“If your own head of civil service was already aware of a formal complaint, it is even more pressing for the Prime Minister to explain what he knew and when, and what questions he asked before choosing the man he would trust to run this country in his absence. .”
Raab, who denies harassment, remains under investigation by attorney Adam Tolley KC, who is believed to have spoken to dozens of officials during his investigation.
Meanwhile, anti-Brexit activist Gina Miller accused Raab of launching an “abusive attack” on her while she was in a BBC studio to discuss Brexit in 2016.
“I can’t decide if you are naive, have too much money or just stupid,” he claimed to have told her, in an article for the Independent website.
Raab was “furious” when a young man told him a car was ready to pick her up, Miller said, adding that he yelled at the man, “Go get me a fucking car.”
“Raab was aggressive and intimidating, and I was bullied and demeaned,” said Miller, who has launched her own political party and plans to run in the next general election.
Downing Street said it is up to Tolley if he decides to investigate his allegation.
But Raab strongly disputed this, with a source close to him saying: “These are baseless and malicious claims, programmed to jump on the political bandwagon and give Gina Miller the publicity she craves.”