Boris Johnson and Jennifer Arcuri enjoyed a simmering sexual tension that blew up into an affair, friends have claimed.
And the PM is alleged to have first “got together” with the US businesswoman in a New York hotel.
It came as cheating Mr Johnson faced claims he groped two women at a lunch while editor of the Spectator.
Downing Street denied all the allegations. But the PM’s estranged wife Marina Wheeler accused him of abusing the trust of all those around him.
Mr Johnson has been referred to police watchdogs over allegations he gave Ms Arcuri, 34, favourable treatment when he was London Mayor.
And the Mirror found 17 gaps in his official diary where he attended “private lunches” at undisclosed locations between 2012 and 2015, covering the period of the alleged affair.
US journalist David Enrich claims he had been told of the apparent fling.
He said: “Two friends from her business class said they had been told by Ms Arcuri that she was sleeping with Boris.”
Mr Enrich told The Sunday Times he heard about the alleged affair while researching a Wall Street Journal story on Ms Arcuri’s business partner in 2013.
One friend told the Mirror: “Jennifer said that she first got together with Boris in a hotel room in New York.
“But she said the sexual tension between them had been building for some time.”
Ms Arcuri’s firm Innotech is said to have been given public money and received privileged access to three foreign trade missions led by Mr Johnson as Mayor.
The Independent Office for Police Conduct is considering whether there are grounds to investigate the 55-year-old for the criminal offence of misconduct in public office.
He refused five times to answer questions over the nature of his relationship with Ms Arcuri during a TV interview.
He insisted: “There was no interest to declare.”
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