Boris Johnson has said he is facing accusations about his personal conduct because he is viewed as the person who is “helping to deliver Brexit”.
The prime minister said it was “inevitable” he would face “shot and shell” because of his stance on Brexit.
He also continued to deny allegations he squeezed a female journalist’s thigh at a lunch 20 years ago.
He said it was “very sad that someone should make those allegations”, adding they were “not true”.
Journalist Charlotte Edwardes, writing in the Sunday Times, accused Mr Johnson of touching her thigh, and that of another woman, at a lunch in 1999 at the offices of the Spectator magazine.
He has also faced questions in recent days over his ties to US businesswoman Jennifer Arcuri during his time as London mayor – he insists he acted with “full propriety”.
It is alleged Ms Arcuri received favourable treatment due to her friendship with Mr Johnson, but the PM has said there was “no interest to declare”.
Asked about stories regarding his personal conduct on the third day of the Conservative conference in Manchester, the prime minister told BBC Breakfast: “I’ve said pretty much what I have to say on all those things.
“This is a very difficult time… Brexit is about to be done and a lot of people don’t want Brexit to be done.
“And I think, rightly or wrongly, they conceive of me as the person who is helping to deliver Brexit, and it is inevitable that I’m going to come under a certain amount of shot and shell.
“I don’t mind that in the least,” he added.
Mr Johnson was also asked about proposals for additional customs checks on the island of Ireland which the UK is said to be taking to the EU.
