Earlier this year, the British government blocked gender reform bills introduced by Scotland.
Amid an ongoing debate on transgender issues, UK Prime Minister Rishi Sunak said in an interview that women do not have penises.
In an interview with ConservativeHome, Mr Sunak was asked about his thoughts on Labour Party chief and Leader of Opposition in the British parliament Sir Keir Stramer's recent statement claiming "99.9 per cent of women of course do not have penises".
"What percentage would you put it at?" Mr Sunak was asked.
The UK PM laughed at the question, however, when grilled about whether he thought the figure was actually 100 per cent, Mr Sunak replied, "Yeah, of course."
"We should always have compassion and understanding and tolerance for those who are thinking about changing their gender. Of course, we should," he said.
"But when it comes to these issues of protecting women's rights, women's spaces, I think the issue of biological sex is fundamentally important when we think about those questions," he added.
Mr Sunak's remarks have surfaced at a time when Britain is debating gender laws issues. The British government is considering plans to create a distinction in equality laws between a person who was born a particular sex and someone who has undergone a sex change.
Kemi Badenoch, UK's minister for women and equalities, wrote to the equalities watchdog Equality and Human Rights Commission, seeking its advice on the "benefits or otherwise" of a proposed amendment to change the legal definition of sex.
"They've responded with some advice about the Equality Act and how it should think about biological sex, we're in the process of looking at that," Mr Sunak said in the interview.
"But as a general kind of operating principle for me, biological sex is vitally, fundamentally important in these questions, we can't forget that. And that's why we need to make sure, particularly when it comes to women's health, women's sports or indeed spaces that we're protecting those rights and those places," he added.
UK's Equality Act allows people from the transgender community to be excluded from single-sex spaces such as changing rooms and shelters.
Earlier this year, the British government blocked gender reform bills introduced by Scotland. The move was slammed by the Scottish authorities who claim their Gender Recognition Reform Bill makes it easier for people to change their legally recognised gender.
The Scottish government on Wednesday announced that it will challenge the blocking of the bills, signalling a legal standoff between the two neighbouring administrations.