Rishi Sunak attacked Sir Keir Starmer for "political opportunism" as the Labour leader quizzed the Prime Minister on Nadhim Zahawi’s tax affairs during PMQs.
The row centres on a tax bill over the sale of shares in YouGov, the polling firm Zahawi founded.
Sunak accused Labour of "clear hypocrisy" for urging him to appoint an ethics advisor then wanting a decision before the adviser had investigated the case.
Starmer told MPs: “I think anybody watching would think it’s fairly obvious that someone who seeks to avoid tax can’t also be in charge of tax. Yet for some reason the Prime Minister can’t bring himself to say that or even acknowledge the question.
“Now, last week the Prime Minister told this House that the chair of the Tory Party had addressed his tax affairs in full and there was nothing to add. This week, after days of public pressure, the Prime Minister now says there are serious questions to answer. What changed?”
Keir Starmer was attacked for 'political opportunism' by Rishi Sunak during PMQs Parliament TV
Sunak replied: “The politically expedite thing to do, would be for me to have said that the matter must be resolved by Wednesday at noon, but I believe in proper due process.
“That’s why I appointed an independent advisor, that’s why the independent advisor is doing his job. But the opposition can’t have it both ways.
“The shadow leader also his party chair, both urged me and the Government to appoint an independent advisor and now he objects to that independent advisor doing their job.
“It’s simple political opportunism and everyone can see through it.”
The Prime Minister asked the independent adviser on ministers’ interests to look into Tory chairman Zahawi’s tax affairs on Monday.
Nadhim Zahawi is set to face an ethics inquiry into his tax affairs Jonathan Brady
The shares in YouGov, worth an estimated £27 million, were held by Balshore Investments, a company registered offshore in Gibraltar and linked to Zahawi’s family.
Sunak says Zahawi will remain Tory Party chairman while he is under investigation over the possible breach of the ministerial code, despite calls to resign.
Allies said on Monday that the former chancellor “absolutely” will not be quitting in the face of growing pressure over his settlement, estimated to be around £5 million.
He has insisted his “error” over shares in the YouGov polling company he co-founded was “careless and not deliberate” .