Foreign Secretary James Cleverly has claimed he can't answer questions on Nadhim Zahawi's tax affairs as he was in the US for work and then "doing some shopping".
The top Tory made the bizarre claim as he was pressed in TV interviews to address reports that Mr Zahawi paid HM Revenue & Customs (HMRC) a seven-figure sum to end a dispute over his tax bill.
Under-fire Mr Zahawi broke his silence yesterday to "address some of the confusion about my finances", admitting a "careless but not deliberate error" related to shares in YouGov, the polling firm he co-founded.
He said he had settled the matter and his tax affairs were up to date when he was appointed as minister without portfolio and Tory chairman by Rishi Sunak.
But the statement stoked fresh questions, including whether Mr Zahawi settled the bill when he was presiding over the country's finances as Chancellor in the summer.
Mr Cleverly floundered when asked about the details, telling the BBC's Sunday with Laura Kuenssberg programme: "I spent the whole of last week in the United States of America and in Canada.
"I arrived back in the UK early on Friday morning, on an overnight flight, before then going on to engage with my constituents through Friday and having a bit of a rest and doing some shopping on Saturday."
He added: "The decision as to how much detail to put in the public domain is rightly one for Nadhim himself."
In a round of interviews, he also said he did not know the size of the tax settlement with HMRC or whether Mr Zahawi paid a penalty.
"I don't know any more detail than is in his public statement," he told Sky's Sophy Ridge on Sunday.
"I'm not an investigator," he added when pressed on why he didn't know more when he had been sent out to speak for the Government.
Asked whether Mr Zahawi will survive until Wednesday, Mr Cleverly said: "What else am I going to say other than yes, because he's a very, very effective minister."
He resisted calls for ministers to be required to publish their tax returns, saying: "I think it's right and proper that people's tax affairs are personal and private."
Mr Cleverly suggested it could put people off going into politics, adding: "We don't demand it of others and if politicians choose to do so, that's great.
"But I think having a unique requirement that is different to the rest of society, I don't think that would necessarily be the best way forward."
Shadow Chief Secretary to the Treasury Pat McFadden said politicians should publish their tax returns.
He said that "I've got no problem with that", adding that he was concerned incidents like this mean the public will think politicians are "all in it for themselves".
Former Tory leader Iain Duncan Smith also suggested Mr Zahawi should “get it all out now” and “clear it up” or questions would continue.
Liberal Democrat Deputy Leader Daisy Cooper said: "These dog ate my homework type excuses simply won't wash with the public. It is a new low for this Government when a senior minister claims he was too busy shopping to read about the main political story of the weekend.
"There are facts that still need to be established so there must be an independent investigation to get to the bottom of this. At a time when the Conservative Government is hiking taxes to record levels, this whole saga comes as a slap in the face to the public. The whole thing stinks."
On Saturday, Mr Zahawi said: "As a senior politician I know that scrutiny and propriety are important parts of public life. Twenty-two years ago I co-founded a company called YouGov. I'm incredibly proud of what we achieved. It is an amazing business that has employed thousands of people and provides a world-beating service.
"When we set it up, I didn't have the money or the expertise to go it alone. So I asked my father to help. In the process, he took founder shares in the business in exchange for some capital and his invaluable guidance. Twenty one years later, when I was being appointed chancellor of the exchequer, questions were being raised about my tax affairs. I discussed this with the Cabinet Office at the time.
"Following discussions with HMRC, they agreed that my father was entitled to founder shares in YouGov, though they disagreed about the exact allocation. They concluded that this was a 'careless and not deliberate' error.
"So that I could focus on my life as a public servant, I chose to settle the matter and pay what they said was due, which was the right thing to do.
"Additionally, HMRC agreed with my accountants that I have never set up an offshore structure, including Balshore Investments, and that I am not the beneficiary of Balshore Investments. This matter was resolved prior to my appointments as chancellor of the duchy of Lancaster and subsequently chairman of the party I love so much. When I was appointed by the Prime Minister, all my tax affairs were up to date."
No10 said it had nothing to add to the statement and said the Prime Minister had confidence in him as Tory chairman.
But opposition MPs have called for an independent probe as well as the publication of all of Mr Zahawi's correspondence with HMRC.
