Boris Johnsons’s adviser on ministerial interests has been contacted by a parliamentary committee over allegations that he was misled by the prime minister over the funding of the refurbishment of his Downing Street flat.

In a letter to Lord Geidt, the crossbench peer who took up the adviser role in April after his predecessor resigned, MPs ask what steps are open to him if he believes he was misled during his inquiry into the handling of the work at the flat.

Geidt’s investigation, which he undertook in May, cleared Johnson of wrongdoing over an apparent £52,000 donation to the Conservatives from a long-standing party donor to cover the costs of redecorating the No 11 residence he shares with his wife Carrie and their two children.

Geidt reported that Johnson told him “he knew nothing about such payments” until February 2021. However, WhatsApp messages that emerged during an Electoral Commission inquiry into the funding showed that Johnson had been in direct contact with the donor, Lord Brownlow, in November 2020. Downing Street sources have suggested Johnson only knew Brownlow was handling the donations, rather than funding them.

William Wragg, the Tory chair of the public administration and constitutional affairs committee, has written to Geidt to ask for his “reflections on several points given the events of the last few weeks”. He states that the Electoral Commission “appears to have had access to information you did not when your own investigation found that [the] ministerial code had not been broken”.

He writes: “What investigatory powers do you have available to you? Are you satisfied that they are adequate and, if so, how do you explain the discrepancy between your findings and those of the Electoral Commission? What steps are open to you if you feel that… you may have been misled?”

He also asks Geidt whether, after six months in the job, he now needs the power to initiate investigations into potential code breaches. Under current rules, he only has the power to ask the prime minister’s permission.

The committee has also asked him how many times he has exercised his right to ask the prime minister’s permission to open an investigation. “Have you used that ‘right’ in relation to the Electoral Commission’s investigation,” the letter states. It goes on to ask: “How satisfied are you that the processes you have followed are sufficient to maintain public confidence that ethical standards are complied with? In the light of your experience of the office and of events of recent weeks, have you now, or will you be, advising the prime minister that the role of the independent adviser needs strengthening and, if so, in what ways?”

Geidt is said to have asked Johnson for the WhatsApp messages exposed by the Electoral Commission. He is also said to have been frustrated by the emergence of the new material, with suggestions that he could consider his position if he concludes he has been misled by the prime minister. Downing Street has confirmed that it was in touch with Geidt.

Should Geidt reopen his investigation, it would be another blow for Johnson, after the byelection defeat in North Shropshire last week and allegations over parties held in Whitehall and Downing Street last year.

A resignation by Geidt would be a further embarrassment. Johnson’ previous ministerial standards adviser, Alex Allan, stood down in November 2020 after the prime minister ignored his findings that the home secretary, Priti Patel, had bullied staff. The parliamentary commissioner for standards, Kathryn Stone, also has the power to open an investigation into the Downing St refurbishment should she believe she has the scope to do so.