reported.
That source also claimed Ms Arcuri would do nothing to shoot down rumours about her links to Johnson - and joked about blondes having "more fun."
A US reporter who wrote a profile on Ms Arcuri's business partner also made similar bombshell claims to the paper.
David Enrich, the financial editor of the New York Times, alleged that Ms Arcuri had revealed to uni friends she was sleeping with Johnson.
Two friends from her business class said they had been told by Arcuri that she was sleeping with Boris
David Enrich Journalist who spoke to Ms Arcuri and her friends He said: "Two friends from her business class said they had been told by Arcuri that she was sleeping with Boris."
And during his research for the 2013 article, Enrich interviewed Ms Arcuri herself - who told him Johnson had warned her about speaking to the press, he alleged.
The Prime Minister, 55, has been plagued by allegations he improperly provided benefits to Ms Arcuri's businesses when he was in City Hall.
He was also forced to deny a claim by a journalist that he groped her leg under a table during a private dinner event in 1999.
Charlotte Edwardes said that the Prime Minister, who was then editor of the Spectator, touched her leg during an event held by the magazine.
She claimed: "He gives it a squeeze. His hand is high up my leg and he has enough flesh beneath his fingers to make me sit suddenly upright."
And the Mirror have reported that Johnson's ex-wife Marina Wheeler views the claims around Ms Arcuri "as an abuse of everyone who has ever trusted him".
A source told the paper: “Marina’s friends say she views the latest allegations about the Arcuri affair along with everything Boris has been doing politically as an abuse of everyone who has ever trusted him.”
She is at the centre of a growing row over £11,500 in public cash granted to her companies by an organisation headed by Johnson at the time.
And Arcuri was also given privileged access to three foreign trade missions in one year - despite her tech firm not meeting the eligibility criteria.
Initial decisions to turn her down for two of the trips were overturned after intervention by Johnson and his close team.
CASH 'SCANDAL' The PM has also been accused of helping her get a further £100,000 in Government grants and sponsorship for her companies.
Johnson was bound by the Greater London Authority's code of conduct to "declare any private interests" relating to his "public duties".
As Mayor, he was also required to take steps to "resolve any conflicts arising in a way that protects the public interest".
He has repeatedly denied any wrongdoing - but has refused to comment on his close friendship with the young Tory campaigner.
Ms Arcuri has denied wrongdoing, but also refused to comment on her personal relationship with Johnson - who now lives with 31-year-old girlfriend Carrie Symonds.
Last night, the couple were seen arriving arm and arm ahead of the Tory conference in Manchester - which threatens to be overshadowed by the scandal.
Tory women come out to defend Boris but admit he's a 'bull in a china shop'
TORY women have this afternoon come out to defend Boris Johnson after he was hit by multiple sleaze allegations today.
Last night it was revealed that the PM allegedly groped a journalist's thigh - and ex-model Jennifer Arcuri was said to have told pals she had an affair with Boris.
And this afternoon ex-Defence Secretary Penny Mordaunt described the PM as a "Frank Spencer in a China shop" but insisted he was a "decent person".
Ms Mordaunt said: "He is not the individual that he is quite often painted as being.
"He occasionally has the style of Frank Spencer in a china shop.
"But he's a decent person. I think he cares a great deal about women and girls.
"And certainly that was my experience when he was foreign secretary."
And Redditch MP Rachel Maclean said: "The original feminists talked about 'deeds, not words'.
"And on that basis, I absolutely judge the Prime Minister to be a feminist.
"And if you look at his record, and what he's done for women - I would point to the record on female genital mutilation, he has been the foremost champion of putting resources into (tackling) that around the world."
Other Tories have refused to comment on Boris' private life.
"Boris has never lectured other people about their private lives," Health Secretary Matt Hancock said earlier.
Boris denied today that he had done anything wrong Boris and Tory supporter Jennifer Arcuri on a campaign battle bus in 2012 Ms Arcuri has denied wrongdoing over the awarding of public cash for her businesses - but has refused to comment on her personal relationship with Boris Johnson Credit: Refer to Caption Boris has been accused of helping Ms Arcuri get access to Government grants and sponsorships totalling more than £100,000 Credit: Refer to Caption Pressure on the PM increased on Friday after the unprecedented move to refer him to the Independent Office for Police Conduct.
They will assess whether there should be a criminal investigation over his relationship with Ms Arcuri.
The referral came from the Greater London Authority (GLA), headed up by Labour mayor of London Sadiq Khan.
Furious Downing Street sources last night hit out at the move , branding it "nakedly political".
A Downing Street Source told The Sun : "Due process has not been followed and the timing is overtly political.
“The public and media will rightly see through such a nakedly political put-up job.”
Environment Secretary Theresa Villiers said the issue had been "blown out of all proportion".
'EVERYTHING DONE PROPERLY' Johnson has previously said that he will co-operate with any investigation into his links with Ms Arcuri by the London Assembly.
The PM has insisted “everything was done entirely in the proper way” over his professional dealings with her.
A No 10 spokesman said: "The Prime Minister, as mayor of London, did a huge amount of work when selling our capital city around the world, beating the drum for London and the UK.
"Everything was done with propriety and in the normal way."
Arcuri said in a statement last week: "Any grants received by my companies and any trade mission I joined were purely in respect of my role as a legitimate businesswoman."
The latest allegations of infidelity follow a string of high-profile stories involving father-of-four Johnson's private life.
He's alleged to have had multiple affairs during his 25-year marriage to second wife Marina Wheeler - including one that resulted in a lovechild.
Lawyer Ms Wheeler filed for divorce last year before Johnson went public with his relationship with former Tory staffer Carrie Symonds.
Defiant Boris Johnson arrived for the Conservative Party Conference in Manchester with girlfriend Carrie Symonds yesterday Credit: Getty Images - Getty Ms Arcuri is now back living in the United States Credit: AFP or licensors Jennifer Arcuri, 34, is a tech entrepreneur and former model Credit: PA:Press Association
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