Boris Johnson's quizzed over 'naughtiest thing' he has done
The Prime Minister said he had not cleared an answer with his "handlers" and would "bitterly regret it" if he improvised one.
During the 2017 general election, then prime minister Theresa May caused amusement after replying that the naughtiest thing she had ever done was to "run through the fields of wheat" as a child.
Mr Johnson, asked the same question on Sky News' Sophy Ridge on Sunday, said: "No, no, no. I'm not telling you the naughtiest thing I've ever done."
Asked why not, the PM said: "Because I would improvise an answer which I had not cleared with my handlers and I would bitterly regret it."
Pressed on whether it was naughtier than running through a field of wheat, Mr Johnson replied: "I'm not going to make any comment about, you know, I'm not, I'm not gonna extemporise some answer about the naughtiest thing I've ever done.
"By the way, I think running through a field of wheat - no, I'm gonna be critical of Theresa."
He added: "I'll tell you what, Sophy, I'll make you this promise.
"If I can think of some answer about the naughtiest thing I've ever done that is both interesting and not terminally politically damaging, I will try and provide it for you the next time we meet."