Prime minister refuses six times to be drawn on ties to Jennifer Arcuri, who received thousands in taxpayers’ money

Boris Johnson has repeatedly declined to comment on reported allegations he failed to declare close personal links to an American woman who received thousands of pounds in public business funding while he was mayor of London.

The prime minister, questioned by reporters on his plane en route to the UN general assembly (UNGA) in New York, refused to answer six questions about his links to Jennifer Arcuri, a US technology entrepreneur.

Asked if he wanted to deny any part of the story, or to comment on the nature of his relationship with Arcuri, Johnson also declined to be drawn.

According to the Sunday Times, a company run by Arcuri received access to money to assist her business, as well as places on trade trips, at times following the intervention of mayoral officials.

The paper also reported that Johnson was, at the time, a regular visitor to Arcuri’s east London apartment, and that she described him at the time as “one of my best friends”.

Asked about the reports, Johnson said: “I’m here to talk about what we’re doing in the UN, and this country’s commitment to tackling climate change, stopping loss of biodiversity and our role in serving as a bridge between our European friends and the Americans when it comes to the crisis in the Gulf.”

The report said Arcuri’s most recent company won a £100,000 government cyber skills grant intended to assist UK firms, even though she has now returned to live in the US. The Department for Culture, Media and Sport has confirmed to the Guardian it is investigating how the money was awarded.

Asked whether a further inquiry might be merited into any potential conflict of interests, Johnson said: “I’m here to talk about, as I said, what we’re going to talk about at the UN.”

Asked whether he and Arcuri had ever had a sexual relationship, Johnson said: “If you’ll forgive me, I’m going to talk exclusively about what we’re doing here at the UN.”

He declined to answer three further questions, including being invited to deny any of the allegations made in the Sunday Times article, saying: “I’m going to talk about what we’re doing in the UN.”

Both Labour and Sir Alistair Graham, the former chairman of the Committee on Standards in Public Life, have said Johnson should answer questions on what happened.

Arcuri’s company Innotech was given £10,000 in sponsorship from a mayoral organisation in 2013, the Sunday Times reported. Johnson was also the guest speaker at several of its events, and appeared in a Google hangout alongside Arcuri.

The report also suggests that Arcuri was initially refused permission to attend two of the trade mission trips because her business did not meet the eligibility criteria.

But after the intervention of Johnson, she was allowed on to the missions, according to an email seen by the paper. It points out that Johnson was bound by a Greater London Authority (GLA) code of conduct to declare any private interests. He was also banned from providing undue benefits to friends.