Boris Johnson has been urged to “fess up” over who paid for his £15,000 luxury Caribbean holiday after a Tory donor denied funding the New Year trip.

Labour has warned the Prime Minister that he must announce who stumped up the money for the getaway or else face a parliamentary investigation.

The PM and girlfriend Carrie Symonds accepted accommodation for a private holiday in St Vincent and the Grenadines as a post-election victory escape.

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Mr Johnson’s entry in the Commons’ register of members’ interests recorded that the trip was paid for by Carphone Warehouse co-founder David Ross.

But multi-millionaire businessman Mr Ross told the Daily Mail he helped put the Conservative Party leader in touch with companies providing accommodation, but denied fronting up the money or the villa.

Labour has called for the PM to provide answers over the trip or else face a parliamentary inquiry.

“Boris Johnson must come clean about who has paid for his luxury trip,” said Jon Trickett, the party’s shadow cabinet office minister.

“If he fails to do so, the Parliamentary Commissioner for Standards should step in and make him fess up.

Mr Johnson’s entry in the Commons’ register of members’ interests recorded that the trip was paid for by David Ross, but the Carphone Warehouse co-founder denies funding the holiday, stating he only helped arrange it.

“The public deserves to know who is paying for their Prime Minister’s jaunts.”

Mr Johnson had already faced criticism at the time for failing to cut the festive break short following the break-out of international tensions when the US killed Iranian general Qassem Soleimani on January 3.

Shadow foreign secretary Emily Thornberry accused Mr Johnson of “sunning himself” while leaving cabinet secretary Mark Sedwill to chair three emergency Cobra meetings about the assassination.

In a declaration published on Wednesday, Mr Johnson announced in the MPs’ register that he had accepted “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, and names Mr Ross as the financial provider.

But Mr Ross told the Mail the former London mayor had asked him for help finding accommodation on the island Mustique, where he and his girlfriend reportedly stayed, but that he had not provided the villa.

A spokesman for the Grimsby-born businessman, reportedly worth more than £650 million, told the newspaper: “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.

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“So Boris got the use of a villa that was worth £15,000, but David Ross did not pay any monies whatsoever for this.”

The jaunt provided Mr Johnson with a break after the election campaign which produced a Conservative landslide for the first time since the 1980s.

A Number 10 spokeswoman said: “All transparency requirements have been followed, as set out in the register of members’ financial interests.”