Members at the FINA Extraordinary Congress voted to require individuals to have completed transition by the age of 12 to compete in women's competitions, effectively banning transgender women if they have gone through any part of the process of male puberty.

Supporters have praised FINA for prioritising fairness in their women's events, while critics including the Federation of Gay Games have described the policy change as "discriminatory and exclusive".

During a visit to Rwanda for the Commonwealth Heads of Government meeting, Johnson backed FINA's decision.

"I haven't studied it in detail but I see no reason to dissent," the Daily Mirror quoted the under-fire British Prime Minister, who earlier this month survived a vote of no confidence from Members of Parliament from his Conservative Party.

Asked whether a woman can be born with a penis, Johnson replied: "Not without being a man.

"That's about as far as I've got on the subject."

Britain's Secretary of State for Digital, Culture, Media and Sport Nadine Dorries said on LBC last week that she would "encourage other sports" to follow FINA's decision.

In contrast, four-time Olympic medallist Daley made his anger towards FINA's decision clear at the British LGBT Awards, where he won the Sports Personality of the Year award.

"I was furious," he said, as reported by iNews.

"You know, like most queer people, anyone that's told that they can't compete or can't do something they love just because of who they are, it's not on.

"It's something I feel really strongly about.

"Giving trans people the chance to share their side."

Daley won Olympic bronze in the men's 10 metres platform at London 2012 and Tokyo 2020.

After a bronze with Daniel Goodfellow in the men's 10m synchronised platform, he claimed Olympic gold in the same event with Matty Lee at Tokyo 2020.

He is also a two-time world champion in the men's 10m platform.

International Federations have been granted more flexibility to set their own policies on the eligibility of transgender athletes in competitions since the International Olympic Committee (IOC) announced a new framework in November of last year.

That followed New Zealand's weightlifter Laurel Hubbard becoming the first openly transgender woman to compete at an Olympic Games at Tokyo 2020.

The IOC's stance has faced renewed criticism following FINA's decision.

FINA's verdict also prompted FIFA and World Athletics to confirm that they will review their eligibility policies, and the International Rugby League to ban transgender players from women's international matches.