According to details recorded in Johnson’s entry in the Commons’ register of members’ interests, the prime minister and girlfriend Carrie Symonds accepted accommodation for a private holiday in St Vincent and the Grenadines.
It stated the gift was from David Ross, a Tory donor who co-founded the Carphone Warehouse chain.
But the Daily Mail reported a spokesman for Ross insisting he was not the owner of the villa and had not paid for Johnson’s stay.
Under the heading “nature and value of benefit in kind (or amount of any donation)”, Johnson’s entry in the register stated: “Accommodation for a private holiday for my partner and me, value £15,000.”
The private holiday lasted from December 26 to January 5, according to the entry in the register.
It provided Johnson with a break after the election campaign which saw him win a Conservative landslide.
At the time Johnson and Symonds went on holiday, it was reported they were visiting the private island Mustique.
A spokesman for Ross told the Mail: “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.”
A Number 10 spokeswoman earlier said: “All transparency requirements have been followed, as set out in the register of members’ financial interests.”
Labour’s 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.”