The prime minister has backed former chancellor Nadhim Zahawi amid allegations he paid millions to settle a dispute over his tax.
Rishi Sunak defended the Conservative Party chairman, saying he had addressed the matter in full after claims he stumped up a seven-figure sum to settle a dispute with HMRC.
Mr Sunak has full confidence in the MP having taken him "at his word" over the allegations, the PM's press secretary said.
Questions have swirled around Mr Zahawi since the Sun on Sunday revealed the tax dispute.
He allegedly avoided tax by using an offshore company registered in Gibraltar to hold shares in the polling company he co-founded, YouGov.
Mr Sunak was dragged into the row at Prime Minister’s Questions when Labour MP Alex Sobel raised the issue.
Mr Sobel said Mr Zahawi was "forced to pay millions to HMRC to settle a tax dispute" and asked Mr Sunak if he was "aware of an investigation when he appointed him to his Cabinet and as chairman of the Conservative Party."
He added: "Will the prime minister demand accountability from his Cabinet members about their tax affairs?"
The prime minister said Mr Zahawi "has already addressed this matter in full and there’s nothing more that I can add".
Mr Sunak’s press secretary said Mr Zahawi "has spoken and been transparent with HMRC”.
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Asked if Mr Sunak is confident he knows everything he needs to know, she responded "yes", giving the same answer when asked whether the prime minister has full confidence in Mr Zahawi.
A spokesman for Mr Zahawi has said that his taxes are "properly declared" and that he "has never had to instruct any lawyers to deal with HMRC on his behalf".
"As he has previously stated, Mr Zahawi’s taxes are properly declared and paid in the UK," the spokesman said.
"He is proud to have built a British business that has become successful around the world."
YouGov’s 2009 annual report showed a more than 10% shareholding by the Gibraltar-registered Balshore Investments Ltd.
The report described the company as the "family trust of Nadhim Zahawi", then an executive director of the polling firm.