Rishi Sunak has been accused of taking a page from the "Boris Johnson playbook" by dragging his feet over demands for an investigation into his Home Secretary.
Suella Braverman stands accused of asking civil servants to help her avoid points on her driving licence for speeding, a possible breach of the ministerial code.
But Mr Sunak has so far resisted opposition calls for a probe into his colleague's behaviour – while a Cabinet minister was sent out to insist on Sunday morning television that government ministers do not “think they are above the rules”.
Appearing at a press conference at the G7 summit in Hiroshima Mr Sunak declined to say he had full confidence in his embattled minister – but said he had not spoken to Ms Braverman and did not know the details of her case.
But he appeared visibly frustrated at repeated questioning by journalists on the issue, asking reporters: "Did you have any questions about the summit?"
Labour and the Liberal Democrats have both called for a probe into Ms Braverman's conduct, led by Mr Sunak's ethics advisor.
The Sunday Times newspaper says the Home Secretary asked officials to organise a private driving awareness course for her – which would have allowed her to avoid both points on her licence and appearing in public with other lawbreakers.
“By refusing to set up an investigation immediately, Rishi Sunak is stealing page one from the Boris Johnson playbook," Ms Braverman's Liberal Democrat counterpart Alistair Carmichael said.
"Time and time again Sunak has put Conservative politicians, who think they are above the rules, in his cabinet and every time they have taken the British people for fools."
Boris Johnson stepped down as prime minister after concerns about his handling of a series of sleaze allegations regarding Tory MPs.
Labour shadow minister Liz Kendall meanwhile pointed out that Ms Braverman had already had to resign once as Home Secretary for breaching the rules, but been reappointed by Mr Sunak anyway.
“I think Rishi Sunak should launch an investigation into it. He should ask his independent adviser whether she has breached the standards of the ministerial code here," she told Sky News's Sophie Ridge on Sunday programme.
"I think a lot of people watching this program will think, why is it always one rule for them and another rule for everybody else?"
Ms Kendall suggested that Ms Braverman was in post because Mr Sundak "had to keep the right wing of his party on board", adding that there was "no point him getting all tetchy at the G7 Press Conference".
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Show all 50Mr Sunak, who pledged a government of “integrity”, has already lost three high-level ministers in seven months – with deputy prime minister Dominic Raab the most recent to quit, following bullying allegations.
Environment secretary Therese Coffey, who represented the government in broadcast media on Sunday, said she was not aware of the details of the case.
But pushed on Ms Braverman's actions, she said: "I don't think Government ministers do think they are above the rules.
"There are people, that I think were referred to earlier, who have recently lost their licence, some people are getting fines.
"We've seen that across all walks of public life. I think what has been written in the newspapers is there, that's the detail that has been shared with the public so far."
But she added: "I don't have any more details than that. Pretty much everybody has the option to pay a fine, take points or go on a course. The precise aspects about the course is what you're trying to speculate, but I don't have any more details than that."
