UK Cabinet Secretary Simon Case was in the dark about Boris Johnson's plans for a charity to take charge of renovating the prime minister's Downing Street flat, The Times reported on Wednesday.
The newspaper cited an unnamed Cabinet Office spokesperson as confirming that Britain's most senior civil servant knew nothing about the matter until UK newspapers disclosed the planned trust in February.
"The cabinet secretary only became aware of the trust in late February. He met Lord Powell and Baroness Jay on 11 March to discuss the facts around the trust. They did not discuss matters relating to historic funding", the spokesperson argued.
They claimed that other civil servants had been in the know about the trust, adding, "cabinet office officials have been engaged and informed throughout and official advice has been followed".
The remarks come after The Guardian reported last week that Johnson asked Case to initiate a review into how the refurbishment of his Downing Street flat was paid for in the wake of previous allegations by Dominic Cummings.
The prime minister's former top adviser asserted in a blog that Johnson's plans for cash from Tory donors to fund the renovation works were "unethical, foolish" and "possibly illegal".
When asked at the time whether he knew about private donations covering costs of the refurbishment, Case said that he had "not been involved directly in this", and that he does not "have all of the facts and details" at his disposal.
Each UK prime minister receives an annual public grant of £30,000 ($41,730) to spend on their living quarters, but the British media reported in February that Johnson and his fiancée Carrie Symonds had spent a whopping £200,000 ($277,400) on refurbishing the flat over 11 Downing Street.
Johnson pledged to comply with the commission's inquiry, insisting that he had "personally" paid for the flat's refurbishment, but declining to clarify whether he received an initial loan from the Conservative Party.
He denied breaking any rules over the matter, claiming that he "conformed in full with the code of conduct and ministerial code".