Boris Johnson has consistently denied any wrongdoing in relation to his friendship with US businesswoman Jennifer Arcuri.
So who is Ms Arcuri and why has the Independent Office for Police Conduct (IOPC) been asked to decide whether to open a criminal investigation into allegations the PM granted her favours when he was London mayor?
On her Twitter page, Ms Arcuri , 34, describes herself as a “fearless entrepreneur” who is “ready to move mountains”.
She is a founder of cybersecurity training firm Hacker House and of Innotech, which has the stated aim of “stimulating the London Tech Scene”.
Ms Arcuri was also reportedly a volunteer on Mr Johnson’s campaign team when he was re-elected as London mayor in 2012, beating Labour’s Ken Livingstone.
A year later Mr Johnson was billed as a keynote speaker at a 2013 Innotech Summit, which also featured “top tech executives in London and Silicon Valley”.
Mr Johnson was pictured at the summit alongside Ms Arcuri, who also accompanied him on trade missions.
His appearance came after a series of messages she sent to the then London Mayor’s adviser Lynton Crosby on Twitter over the preceding few weeks.
Not long before the summit, Ms Arcuri also took to Twitter to defend Mr Johnson following a TV interview during which presenter Eddie Mair described him as a “nasty piece of work”.
Ms Arcuri tweeted: “amazin leader: @BorisJohnson personal biz:NOT 4 public2judge: those quest were asked maliciously”
During the Innotech summit, Mr Johnson took part in what was described as his first Google Hangout and also appeared in icing form on a cake shown off by Ms Arcuri to mark the occasion.
Later that year she posed for photos drinking tea with Mr Johnson as they discussed a “new fund 4 global talent 2 build gr8t tech companies”, according to her tweets.
And in 2014 she posted pictures from a number of Mr Johnson’s speaking events – including a trade mission which took him to Singapore and Malaysia.
Details of her links to Mr Johnson were highlighted in the Sunday Times last week, which reported that Ms Arcuri was given £126,000 in public money and privileged access to three foreign trade missions led by Mr Johnson while he was mayor.
Mr Johnson also visited Ms Arcuri’s then home, a flat in London’s fashionable Shoreditch district, which featured a pole-dancing pole, according to reports.
On Friday, the Greater London Authority (GLA), which is now headed by Labour mayor Sadiq Khan, said its monitoring officer had recorded a “conduct matter” against Mr Johnson and the IOPC was considering whether there were grounds to investigate for the criminal offence of misconduct in public office relating to the then mayor in his role as police and crime commissioner for London.
The move was greeted with fury in Downing Street, which denounced it as a “nakedly political put-up job” on the eve of the Tory Party conference in Manchester.
But in a statement, the GLA said that the monitoring officer, Emma Strain, had a “statutory duty” to record any conduct matters which she became aware of.
The statement said: “The ‘conduct matter’ has been recorded as allegations have been brought to the attention of the monitoring officer that Boris Johnson maintained a friendship with Jennifer Arcuri and as a result of that friendship allowed Ms Arcuri to participate in trade missions and receive sponsorship monies in circumstances when she and her companies could not have expected otherwise to receive those benefits.
“A ‘conduct matter’ exists where there is information that indicates that a criminal offence may have been committed. It does not mean that this is proved in any way.
“The IOPC will now consider if it is necessary for the matter to be investigated.”
Meanwhile, the UK Government has frozen a grant to Ms Arcuri’s company, Hacker House, pending a review.
It is facing questions about the verification process carried out before awarding the money to a company whose directors are based in the US.
Digital Minister Matt Warman told the Commons earlier this week that his culture, media and sport department (DCMS) had done the “usual due diligence” and that the company had a British phone number.
However, numerous reports said calls to the number were directed to an office in California.
Ms Arcuri’s British husband and Hacker House co-director Matthew Hickey defended the grant on Twitter, saying: “It was awarded for development of our portal (which is up and running, maybe that should be news?).
“We employ several British people who work on it.
“There’s nothing improper about it and we have been regularly updating DCMS and working with UK government on its needs. ”
Hacker House was incorporated in July 2015 according to Companies House records, which lists Ms Arcuri’s occupation as an “ethical hacker” and her country of residence as the US.
Ethical hacking involves exploiting IT systems with the permission of the owners to find weaknesses.
According to her LinkedIn profile, Ms Arcuri, 34, has an MBA from the Hult international Business School in the US and also studied at the University of Southern California, Pace University’s Lubin School of Business and the University of Wisconsin-Madison.
Her Twitter page gives her locations as London, San Francisco and Los Angeles.