- Johnson intervened in favour of Jennifer Arcuri - a model turned tech entrepreneur - who worked on Johnson's campaign for Mayor of London and became a close friend.
- He was reportedly seen visiting Arcuri's flat on multiple occasions.
- The opposition Labour party call on the prime minister to answer questions about his use of public money.
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Boris Johnson reportedly overruled officials to send a close friend on foreign trade missions, despite her business failing to meet eligibility criteria for the visits.
Jennifer Arcuri, who set up the tech firm Innotech, was also handed multiple grants by public bodies totalling more than 100,000, including an agency set up by Johnson, according to the Sunday Times.
The paper reports that Johnson formed a "close friendship" with Arcuri, who worked on his campaign for Mayor was seen repeatedly visiting her flat in Shoreditch, London.
Johnson failed to declare the potential conflict of interest despite being obliged to by strict City Hall code of conduct rules.
Arcuri, who is a former model turned tech entrepreneur, was handed a 10,000 grant by an agency set up by Johnson and he attended multiple events organised by Arcuri.
She was sent on a series of trade missions, despite failing to meet the criteria for the trips, according to the paper. The Sunday Times reports that Johnson's office intervened on two occasions to overrule officials to ensure her attendance.
The paper reports that Arcuri was awarded a 100,000 grant earlier this year by the Department for Digital, Culture, Media and Sport intended to help British businesses.
The grant is now reportedly the subject of a departmental investigation after the Times discovered that Arcuri's company's registered address is a rented house in Cheshire with Arcuri now living in California.
In a statement Arcuri told the Sunday Times that: "Any grants received by my companies and any trade mission I joined were purely in respect of my role as a legitimate businesswoman...
"I am incredibly disappointed that The Sunday Times cannot write about a successful female entrepreneur without smearing her with innuendo based on leaks from City Hall."
The paper reports that she declined to answer questions about the nature of her friendship with Johnson.
Jon Trickett, Labour's Shadow Minister for the Cabinet Office, said Johnson should answer questions about his use of public money.
"Boris Johnson must now give a full account of his actions in response to these grave and most serious allegations of the misuse use of public money in his former role as mayor of London," he said.
"This cannot be swept under the carpet. It is a matter of the integrity of the man now leading our country, who appears to believe he can get away with anything
"The public has a right to know how and why these funds were used for the benefit of a close personal friend without on the face of it legitimate reason.
"This cannot be swept under the carpet. It is a matter of the integrity of the man now leading our country, who appears to believe he can get away with anything."
A spokesperson for the prime minister was contacted for comment.