Video report by ITV News Correspondent Richard Pallot
Labour has formally written to the Parliamentary Commissioner for Standards calling for an investigation into who paid for Boris Johnson’s £15,000 trip to the Caribbean.
The prime minister claimed in the Commons' register of members' interests that the holiday was paid for by Tory donor David Ross.
But a spokesperson for the Carphone Warehouse co-founder denied Mr Ross fronted up any cash for the villa, instead saying that it was a "benefit in kind".
"Mr Ross facilitated accommodation for Mr Johnson on Mustique valued at £15,000," the spokesperson said.
"Therefore this is a benefit in kind from Mr Ross to Mr Johnson, and Mr Johnson's declaration to the House of Commons is correct."
Despite the clarification, Shadow Cabinet Office minister Jon Trickett penned a letter to Kathryn Stone requesting she look into details of Boris Johnson’s luxury holiday, which took place over the new year.
The senior opposition MP said he remained dissatisfied with the explanations provided by Downing Street.
In his letter to the commissioner, Mr Trickett said: “The Code of Conduct requires members to provide the name of the person or organisation that actually funded a donation.
“The evidence now suggests it was not David Ross. The entry made by the Prime Minister therefore appears to be incorrect.”
Mr Trickett said the public should know whether the PM “knowingly make a false entry into the register”.
Labour earlier said Mr Johnson should face a parliamentary investigation unless he revealed who paid for the trip.
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 named Mr Ross as the financial provider.
Mr Ross earlier told the Daily Mail the former London mayor had asked him for help finding accommodation on the island of Mustique, where he and his girlfriend reportedly stayed, but that he had not provided the villa.
A spokesperson 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.
"So Boris got the use of a villa that was worth £15,000, but David Ross did not pay any monies whatsoever for this."
Mr Tricket said it was "crucial" for the prime minister's finances to be transparent and urged the commissioner to investigate the PM.
"Ttransparency is crucial to ensuring the public have confidence that elected members of this House have not been unduly influenced by any donations or gifts that they may receive.
“For this reason, I request that you to investigate whether the Prime Minister has followed all transparency requirements when registering the donation.”
A Downing Street source said much of what was being alleged by Mr Trickett had been made “out of date” by the updated statement by Mr Ross’ spokesman.
“What is being said in the letter has been covered off by additional statements made by David Ross’ spokesman,” the source told the PA news agency.
The holiday 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 spokesperson said: "All transparency requirements have been followed, as set out in the register of members' financial interests."
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.