LONDON — A monitor at London’s City Hall has referred Prime Minister Boris Johnson of Britain to a police watchdog for a possible investigation of claims that he unduly favored an US entrepreneur while mayor of the city, intensifying a politically risky scandal as he faces a hostile Parliament and a looming Brexit deadline.
The official said the claims about Johnson’s ties to the entrepreneur, Jennifer Arcuri, who joined several of the mayor’s international trade missions and whose businesses were awarded tens of thousands of pounds in government money, were a “conduct matter” — essentially “an indication” that he may have committed “a criminal offense.”
The government’s response was fierce and dismissive: A Cabinet minister from Johnson’s Conservative Party, Theresa Villiers, told the BBC on Saturday that it was “an obviously politicized complaint.”
Several British news outlets earlier quoted an unnamed government source as calling the referral “a nakedly political put-up job,” one done without warning to Johnson and without following due process.
Both Johnson and Arcuri have denied any wrongdoing.
The referral does not necessarily mean the prime minister will be investigated. The Independent Office for Police Conduct confirmed that it had “received a referral from the monitoring officer of the Greater London Authority regarding a conduct matter against Boris Johnson.”
But it added in a statement, “This will take time to thoroughly assess and consider before any decision is taken as to whether it is necessary to investigate this matter.”
The referral letter was attributed to the Greater London Authority’s monitoring officer, Emma Strain, a career official who worked at City Hall in other roles during Johnson’s tenure as mayor.
A City Hall spokesman did not immediately respond to requests for comment Saturday.
The letter said she was legally obligated to refer Johnson to the police watchdog because she had been made aware of accusations that, if true, could amount to an offense of misconduct in public office.
“During this time it has been brought to my attention that you maintained a friendship with Ms. Jennifer Arcuri, and as a result of that friendship allowed Ms. Arcuri to participate in trade missions and receive sponsorship monies in circumstances where she and her companies could not have expected otherwise to receive those benefits,” the letter said.
But the letter added that it was not the monitoring officer’s role “to investigate or determine whether any offense has been committed. Similarly, I do not investigate the veracity of the allegations or whether they are substantiated.”
The letter did not mention who had passed on the accusations to the monitoring officer.
On Tuesday, the elected London Assembly asked Johnson to explain his relations with Arcuri, and on Friday, he said he would comply.
Arcuri, a former model, was 27 when her path first crossed Johnson’s in 2012.
According to The Sunday Times of London, which first reported the matter last weekend, Johnson also made afternoon visits to the apartment where Arcuri then lived in Shoreditch, in East London, while on breaks from his duties as mayor. The article was illustrated with a photograph of Arcuri using a dancing pole fitted in her home.
A subsequent explanation for the visits — that the mayor had been receiving technology lessons — prompted mockery on Twitter and in Parliament.
One of Arcuri’s businesses, Hacker House, was awarded a central-government grant of 100,000 pounds (more than $120,000) in February, before Johnson became prime minister.
Matt Warman, a junior culture minister, told lawmakers that Johnson had no role in the awarding of that grant. But the national Department for Culture, Media and Sport is reviewing the grant following reports that Arcuri had moved back to the United States and her business might not be sufficiently British based to qualify for the money.
Johnson told a reporter from the broadcaster ITV, “Absolutely everything was done with full propriety and in accordance with proper procedures.”
But that has done little to tamp down speculation about Johnson, whose sometimes turbulent personal life has frequently made headlines in Britain.