Boris Johnson’s Christmas paradise getaway was a £15,000 gift from the founder of Carphone Warehouse, it emerged.
According to the Prime Minister's register of interests Tory donor David Ross lent Mr Johnson and girlfriend Carrie Symonds his luxury bolthole for 11 days over the festive break.
At the time the pair went on holiday, it was widely reported they had escaped to the private island of Mustique - a favourite of Prince William and the Duchess of Cambridge.
The mystery of who was behind the Conservative leader’s New Year break was finally solved in a regular update to the PM’s Register of Interests.
But last night Mr Ross denied that the pair had stayed in his house on the luxury island.
He told the Daily Mail he had been asked for help to find the PM accommodation for his break but had not "put his hand in his pocket".
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Under the heading “nature and value of benefit in kind (or amount of any donation)”, Mr Johnson’s entry on the official register stated: “Accommodation for a private holiday for my partner and me, value £15,000.”
The break lasted from December 26 to January 5, according to the entry in the register.
Labour asked the Parliamentary Commissioner for Standards to launch an investigation to find out who was behind the donation.
Shadow cabinet office minister Jon Trickett said: "Boris Johnson must come clean about who has paid for his luxury trip.
"If he fails to do so, the Parliamentary Commissioner for Standards should step in and make him fess up.
"The public deserves to know who is paying for their Prime Minister’s jaunts."
A spokesman for the businessman said: "Boris Johnson did not stay in David Ross’s house.
"Boris wanted some help to find somewhere in Mustique, David called the company who run all the villas and somebody had dropped out.
"So Boris got the use of a villa that was worth £15,000, but David Ross did not pay any monies whatsoever for this.’
Asked about Mr Johnson’s declaration, the spokesman said: "I believe it is a mistake."
He added that Mr Ross had "not put his hand in his pocket whatsoever and can obviously prove that – [he] most definitely did not pay anything and it was not his house.
"It was a house that was rented but the people could not turn up, so Boris Johnson got the use of it."
