Boris Johnson has "full confidence" in his embattled Chancellor after a row broke out over his family's finances.
A spokeswoman for the Prime Minister also confirmed that Downing Street had accepted Rishi Sunak's request for an investigation by Lord Geidt, Johnson's independent adviser on ministerial interests.
Asked if Boris Johnson continues to have "full confidence in the Chancellor", a No 10 spokeswoman said: "He does."
In a letter to the Prime Minister, Sunak asked for Lord Geidt to review all his declarations of interest since he became a minister in 2018 to ensure they had been properly stated.
Asked if Lord Geidt had begun his investigation into the Chancellor, the spokeswoman said: "I'm not aware of whether Lord Geidt himself has begun his work.
"But I can confirm that the Prime Minister has agreed to the request from the Chancellor for Lord Geidt to undertake this work."
Sunak said he was confident he had acted appropriately at all times, but his "overriding concern" was that the public should have confidence in the answers.
The Chancellor visited Darlington on Monday in an attempt to show he was getting on with the job of being Chancellor, naming the final two sites in the running for the Treasury's outpost in the town.
Cabinet colleague George Eustice said Sunak was the Chancellor "at the moment" and had paid all relevant UK taxes.
Sunak's political career is at risk of being derailed by the row over his wife's non-domiciled status and his own former holding of a US green card.
The Chancellor's decision to request an investigation by Lord Geidt was the latest attempt to defuse the political storm that has engulfed him.
An announcement on Friday by his wife, Akshata Murty, that she would pay UK taxes on all her worldwide income failed to stem the criticism.
Environment Secretary Eustice faced questions from broadcasters on Monday about the row.
Sunak had been "very clear that he's been very candid about his own arrangements at every stage", Eustice told Sky News.
Eustice rejected suggestions that Sunak was "too rich" to be a chancellor or potential prime minister.
"I don't think it's right that we should have a rule that says you're too wealthy to be able to do a role - what matters is the knowledge, the technical expertise that you have," he told BBC Radio 4's Today programme.
"You can't walk a mile in everyone's shoes, all of us have different perspectives, different experiences in life, and for any MP, let alone minister, the single most important thing is an ability to empathise (with) people who might have had experiences and challenges in their life that you've personally not experienced."
But Labour continued to press for answers on Sunak's arrangements and his wife's business interests.
It has been estimated that her non-dom status could have saved her £20 million in taxes on dividends from her shares in Infosys, an Indian IT company founded by her father.
Public records show Infosys has received more than £50 million in UK public sector contracts since 2015 - with Labour arguing Sunak should have registered an interest in the firm, because of his wife's involvement.
Sunak has ordered a full-scale investigation by the Cabinet Office and the Treasury into who leaked details of his wife's tax status to the Independent, which triggered the row.
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