Boris Johnson should pay back his taxpayer-funded legal fees for the Partygate inquiry and an investigation into “issues” with the Cabinet Office’s sign-off process should be launched, Labour has said. Pat McFadden, the shadow chancellor of the Duchy of Lancaster, said the £265,000 bill should be looked into after a critical report was published this week by the National Audit Office. The public spending watchdog found the proper process was not followed when the Cabinet Office agreed to cover Johnson’s legal bills last August, because the decision was not made by the correct accounting officer. It found the correct official did endorse the decision, but a month after it had already been taken. The NAO also said the precedents cited by the government for covering the costs during the privileges committee’s inquiry were not “wholly persuasive”. McFadden wrote to William Wragg, the Conservative MP and chair of the public administration and constitutional affairs committee, calling for him to launch an inquiry into the process. Highlighting the NAO’s finding that other legal cases where ministers had their legal costs covered were “substantively different” from the Commons probe, McFadden said: “I would very much agree.” He added there were several “issues with Cabinet Office processes” identified and that there was “legitimate public interest in terms of the sums of money involved, their use and the approval processes for agreeing this”. McFadden asked the committee, which examines the work of the Cabinet Office, to look at whether the use of taxpayers’ money was appropriate. He also said the committee should examine whether the flawed process was “inconsistent with good government practice” and “whether the funds should be returned, as we have previously called for”. Johnson declined to comment. Since leaving No 10, he has made millions of pounds through a combination of speeches and books, and been gifted tens of thousands in-kind for hospitality and accommodation. A Cabinet Office spokesperson said: “There is an established precedent across multiple administrations based on the principle that former ministers, of all political colours, may be supported with legal representation after they have left office – when matters relate to their time and conduct as a minister of the crown. “The government has been consistently clear that the contract award followed the proper procurement process.” The cross-party privileges committee concluded in the summer that Johnson had misled parliament. Its findings prompted Johnson to quit as an MP before sanctions could be imposed.