The Sunday Times reported that the American businesswoman – whose companies have been awarded a total of £126,000 in state funding – had repeatedly told friends she had an intimate relationship with Mr Johnson while he was at City Hall.
On Friday, the prime minister was referred to the Independent Office for Police Conduct to assess whether he should face a criminal investigation for misconduct in public office. A Department for Digital, Culture, Media and Sport investigation is under way into a £100,000 grant made to a company run by Ms Arcuri.
In an interview on BBC1’s Andrew Marr Show, Mr Johnson was asked whether he declared an interest under the Greater London Authority’s code of conduct over the award to Ms Arcuri of public money and privileged access to mayoral trade missions.
He replied: “There was no interest to declare.”
And he added: “Everything was done in accordance with the code ... and everything was done with full propriety.”
The prime minister suggested that the Arcuri issue was being used by opponents of Brexit in a bid to undermine his ability to take the UK out of the EU on 31 October.
“I’ll tell you want I really think is going on,” he said. “There is a large constituency in parliament and elsewhere who do want to frustrate that objective and, rightly or wrongly, they see me as the person most likely to deliver that objective.
“If you are in my position, you have got to expect a lot of shot and shell.”
Mr Johnson was not asked during the interview about the Sunday Times report, which quoted US journalist David Enrich as saying he had been told of an alleged intimate relationship between Mr Johnson and Ms Arcuri by two of the businesswoman’s friends.
His account was said by the newspaper to corroborate that of other sources who had spoken to Ms Arcuri.
Downing Street refused to comment on the report.
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