Downing Street has denied a claim that Boris Johnson squeezed a female journalist’s thigh under the table at a private lunch.
Writing in the Sunday Times, Charlotte Edwardes said the incident happened to her at the offices of the Spectator magazine in 1999.
A Number 10 spokesman said: “This allegation is untrue.”
But Ms Edwardes said if the PM “doesn’t recollect the incident then clearly I have a better memory than he does”.
In her first column for the Sunday Times, published on the eve of the Conservative conference in Manchester, Ms Edwardes said she was seated on Mr Johnson’s right.
“More wine is poured; more wine is drunk. Under the table I feel Johnson’s hand on my thigh. He gives it a squeeze.
“His hand is high up my leg and he has enough inner flesh beneath his fingers to make me sit suddenly upright.”
Ms Edwardes said another woman at the lunch later told her he had done the same to her.
Mr Johnson was editor of the Spectator at the time.
Earlier in the day, Health Secretary Matt Hancock appeared to play down the claims.
He said Mr Johnson “has never lectured other people about their private lives” adding: “I think that we should concentrate on delivering on what we are in politics for, which in my view is to serve the citizens of this country.”
Later, though, in an interview with Channel 4 News – conducted before No 10 issued its denial – Mr Hancock stressed that he did not intend to make light of Ms Edwardes’ allegations.
“I don’t dismiss it at all. I have seen how what I said has been… how people have responded to what I said, and [to be] totally clear about it, these issues are incredibly important.”
Asked whether he believed Ms Edwardes, the health secretary replied: “I know Charlotte well and I entirely trust what she has to say. I know her and I know her to be trustworthy.”
Former cabinet minister Amber Rudd also gave her support to Ms Edwardes.