Boris Johnson was left flustered when he was asked how many children had attended state school during a radio Q&A this morning.
The Prime Minister has been fiercely protective of his private life and it is not public knowledge how many children he has.
Rachel Burden, hosting a Q&A with listeners on BBC 5Live, brought up the touchy subject while discussing education funding.
Ms Burden said many viewers want Johnson to be asked how many children he has.
But the BBC presenter did not put the question to him directly, and he chose not to address it.
She did ask the PM: "Do you have any children of school age?"
To which Johnson replied: "Sorry, I don't comment about my children. I'm not going to comment on my children, if that's alright."
Ms Burden said the topic of Mr Johnson's children is a "question that frequently comes up".
She told him: "Lots of people have been in touch this morning saying, 'ask the Prime Minister how many children he has'.
"That is a question that frequently comes up, just so you're aware.
"I think people find it odd that someone who is a public figure can't answer that question."
But he did later say at least one of his unconfirmed number of children had been to a state school.
He said: “Your assertion that none of my children have been to state school is wrong. That's all I'll say."
Johnson has split from wife Marina Wheeler with whom he had four children and is currently dating Carrie Symonds.
Johnson and Ms Wheeler, who married in 1993, have four children together - Lara, Milo Arthur, Cassia Peaches, and Theodore Apollo.
But he has had multiple affairs, including the one with Petronella Wyatt which led to a pregnancy that was terminated.
And a 2013 court ruling said the public were entitled to know about claims that one affair - with art consultant Helen Macintyre - resulted in a daughter who was his.
The child's family had sought to stop the father being named.
But the Court of Appeal said: “The core information in this story, namely that the father had an adulterous affair with the mother, deceiving both his wife and the mother's partner and that the claimant, born about nine months later, was likely to be the father's child, was a public interest matter which the electorate was entitled to know when considering his fitness for high public office."
Asked finally about his plans for Christmas, the Prime Minister said he had not had time to make arrangements because he was "so determined to get Brexit done".
"I am afraid, literally, I haven't had a chance to think about it," he said.
