A British parliamentary standards committee on Thursday cleared Prime Minister Boris Johnson of breaching a lawmakers' code of conduct over a luxury Caribbean holiday, but criticised his handling of the matter.

After a months-long probe, the House of Commons Committee on Standards concluded Johnson had accurately declared how he paid for the controversial trip with his then fiancee -- now wife -- Carrie Symonds to the privately owned island of Mustique over Christmas 2019.

However, the cross-party panel of MPs said it was "regrettable" that a full explanation of the opaque arrangements that saw a Conservative Party donor fund their holiday accommodation had not been provided earlier.

It noted the British leader has been previously admonished over other financial interest declarations, and urged all lawmakers "to avoid seeking or accepting gifts or hospitality on the basis of complex and unclear funding arrangements".

"This matter could have been concluded many months ago if more strenuous efforts had been made to dispel the uncertainty," the committee stated in a 47-page report on its probe.

"Given that Mr Johnson was twice reprimanded by our predecessor Committee in the last Parliament in the space of four months for 'an over-casual attitude towards obeying the rules of the House', we would have expected him to have gone the extra mile to ensure there was no uncertainty about the arrangements."

Johnson has faced multiple watchdog investigations over various issues since becoming prime minister in 2019, and has long been dogged by questions about the luxury holiday.

In the register of MPs' interests, he claimed the 15,000 pounds ($21,200) worth of accommodation on the island was provided by David Ross, a businessman and donor to his ruling Tory party, who owns a villa there.

However, the committee was asked to investigate following a complaint that Johnson had inaccurately or only partially declared how the trip was paid for, amid reports he stayed in a different property.

The investigating lawmakers, and a separate probe by the Parliamentary Commissioner for Standards Kathryn Stone, found Johnson did stay in another villa.

The report notes they eventually discovered there was "an ad hoc agreement in place" for Ross to subsequently provide the use of his own villa to the island's management company to compensate for the cost of alternative accommodation.

"It is regrettable that a full account and explanation of the funding arrangements for Mr Johnson's holiday accommodation has only come to light as a result of our own enquiries rather than at an earlier stage," the report said.