Britain's prime minister under investigation for holidays in the Caribbean: He said he paid Ross, he said no.

Parliamentary standards commissioner Kathryn Stone confirmed Monday morning that she was investigating a possible violation of the MP's code of conduct.

Downing Street has earlier said that “all relevant transparency requirements” have been met around the trip to Mustique, a private island in the Archipelago of San Vincent and Grenadine.

The Daily Mail reported that Johnson spent 10 days in luxury villas worth 15,000 pounds. At first, the prime minister said he had accepted the accommodation for a private vacation with his partner, worth 150,000 pounds, citing conservative donor David Ross.

But a spokesman for Mr. Ross, the cofounder of Carphoone Warehouse, denied he had paid for it.