U.S. Businesswoman Admitted Affair With Boris Johnson, U.K. Report Says

Earlier, The Sunday Times reported that Mr. Johnson often paid afternoon visits to the apartment where Ms. Arcuri lived in East London while on breaks from his duties as mayor. The article was illustrated with a photograph of Ms. Arcuri using a dancing pole fitted in her home.

Mr. Johnson gave Ms. Arcuri’s first venture a major lift by appearing at four networking events for entrepreneurs and policymakers that her company had organized, the newspaper said.

She received 11,500 pounds, or around $14,000, in sponsorship money from an organization that was overseen by Mr. Johnson as mayor. And she was given coveted spots on trade missions with the mayor to Malaysia, New York, Singapore and Tel Aviv. In some instances, Mr. Johnson’s office intervened to add her to the roster even though she did not meet the criteria for trade delegates, the report said.

Another business later set up by Ms. Arcuri, Hacker House, was awarded a central government grant of £100,000, about $120,000, in February, before Mr. Johnson became prime minister.

An unnamed Conservative Party activist told the newspaper that Ms. Arcuri had acknowledged the affair and that, even when other people were around, played along with jokes about their status.

After initially declining to discuss the accusations, Mr. Johnson told a reporter from the broadcaster ITV, “Absolutely everything was done with full propriety and in accordance with proper procedures.”

Mr. Johnson’s serial philandering has frequently made headlines in Britain. Earlier in his career, he was fired from the Conservative Party’s leadership team after falsely denying reports of an extramarital affair.

But the new accusations have put Mr. Johnson under a level of scrutiny that he has rarely received during his turbulent career.