Rishi Sunak is under intense pressure to launch an investigation into whether Suella Braverman broke the ministerial code by requesting a private speed awareness course, as Downing Street appeared to distance itself from the beleaguered home secretary. The prime minister arrives back from the G7 summit in Japan to a growing political storm over whether Braverman breached strict rules by asking Home Office civil servants for special treatment after she was caught breaking the speed limit. He will have to quickly determine whether to ask his ethics adviser, Sir Laurie Magnus, to investigate. Downing Street confirmed Sunak will consult with Magnus when he returns from Japan. Braverman is due to appear before MPs for Home Office questions on Monday, Labour is expected to table an urgent question and Conservative ministers, MPs and aides are in mutinous mood over her survival. One senior Tory source said there was “no appetite” in No 10 to defend the home secretary. “It’s a totally unforced error,” they added. Downing Street insiders even suggested they were content with Braverman “blowing herself up”, but said there was not yet an appetite to make an overt move against her. At a press conference at the end of the G7 summit, the clearly frustrated prime minister ignored questions about whether he should order an ethics inquiry into Braverman’s conduct but stopped short of saying he had full confidence in her. Sunak told reporters that he had not spoken to the home secretary after the revelations and claimed he did not know the details. However, he added: “I understand she has expressed regret for speeding, accepted the penalty and paid the fine.” Yet the prime minister is certain to face questions when he lands in the UK over whether he was aware of the home secretary’s attempts to arrange a private speed awareness course. The cabinet secretary, Simon Case, is not believed to have been aware of the matter. Under the proposal, Braverman would not have had to attend an in-person course with other motorists, or an online one where her name and face would be visible on camera to other participants. Sources claimed that Home Office officials emailed the Cabinet Office’s propriety and ethics team to ask whether they could advise the home secretary. They were immediately told they could not. When the civil servants refused to help, Braverman is believed to have turned to a political aide who tried to persuade the course provider to agree to the proposal. When they declined, she opted to take the three points on her licence and pay the fine instead. One source said that the Home Office had pushed to release a statement at the weekend, in advance of revelations published in the Sunday Times, saying that Braverman had followed due process by seeking appropriate advice from officials. However, there was “strong pushback” from No 10, which felt it needed more time to establish the facts. The Cabinet Office would usually be responsible for statements on such issues. The former Tory party chair Jake Berry said Braverman had “questions to answer”. Sources close to Braverman suggested that she had simply asked officials for advice on how to arrange a driving awareness course. This is understood to have included raising the possibility of a private course, although it has been denied that she directed them. The prime minister’s ethics adviser could request all emails and messages sent between departments if he is asked to investigate the matter. One source said that Braverman’s request to officials was in email form, meaning Magnus could see it. Ministers are banned from directing civil servants to help with their personal affairs under the code, which states that they have a personal obligation to ensure that “no conflict arises, or appears to arise between their personal interests and public duties”. They are also expected to abide by the Nolan principles of public life, which set ethical standards for ministers and are written into the ministerial code. There is now a range of sanctions available for ministers who are in breach. Dave Penman of the FDA union, which represents senior officials, said: “Any approach to civil servants on what is a purely personal matter is inappropriate, but as a former attorney general and as the current home secretary, Braverman should be aware of the implications of asking civil servants’ advice or to intervene on this issue and the obvious conflicts of interest that arise. “That Home Office civil servants appear to have sought advice from the Cabinet Office, and subsequently refused the request, would suggest that serious concerns were being raised by this. “As sole arbiter of the ministerial code, the prime minister alone gets to decide whether there is an investigation. This raises questions once again about what he knew about his minister’s conduct and when.” The home secretary has already been sacked once from the role under Liz Truss, because she sent an official document from her personal email to a fellow MP in a serious breach of ministerial rules. Sunak reappointed her six days later. However, it could be problematic for the prime minister to have his home secretary in peril the same week that the latest migration statistics are expected to show that net legal migration has risen from 500,000 and hit an all-time record. On his final day at the G7 summit, Sunak said that he thought overall migration numbers were “too high” and said he was “committed to bringing them down”. He had earlier set a new goal of bringing migration down below the level he “inherited”, which was about 500,000 net arrivals a year when he became prime minister. The Guardian has learned that Braverman tried to get out of the final Commons vote on the government’s small boats bill despite Conservative MPs being instructed to attend on a three-line whip. The home secretary’s aides sent multiple emails over the course of several days to the Tory whips’ office requesting that she be slipped for the third reading of her department’s headline legislation. Sources said that the chief whip, Simon Hart, had to call Braverman directly to instruct her to attend the vote on the illegal migration bill. A source close the home secretary said: “This is a load of drivel.”