The Prime Minister has waded into the transgender debate by coming out on the side of biology.
Boris Johnson said during Prime Minister's Questions on Wednesday that transgender people should be treated with generosity and respect.
But he also argued that biology cannot be ignored.
"We must recognise when people want to make a transition in their lives that they should be treated with the maximum possible generosity and respect," he said.
On the question of "distinguishing between man and woman", though, he said that "the basic facts of biology remain overwhelmingly important".
His comments contrast with those of opposition leader Sir Keir Starmer, who in the past has claimed that it is "not right" to say that only women have a cervix.
"It is something that shouldn't be said. It's not right," he said on the BBC's The Andrew Marr Show last September.
Earlier this month, Sir Keir reiterated his stance by saying that "trans women are women".
He was criticised by Harry Potter author JK Rowling among others over his comments to The Times newspaper.
