Rishi Sunak has stood by Nadhim Zahawi amid a row over the Conservative Party chairman's tax affairs.
Jim Harra, HMRC's chief executive, suggested on Thursday morning that Mr Zahawi had not made an "innocent error", telling MPs: "There are no penalties for innocent errors".
Mr Sunak has launched an ethics probe into the matter after it emerged the Tory chairman had resolved a multimillion-pound tax dispute by paying a penalty.
Speaking after an away day at Chequers, his grace-and-favour residence, the Prime Minister told "I'm not going to pre-judge the outcome of the investigation, it's important that the independent adviser is able to do his work.
"That's what he's currently doing, that's what I've asked him to do and I'll await the findings of that investigation."
Mr Sunak gave a similar answer when asked about a separate investigation into Dominic Raab, the Deputy Prime Minister, over his alleged behaviour towards civil servants and officials across three departments.
