Swimming's world governing body has voted to effectively ban transgender athletes from competing in women's elite races.

FINA will explore establishing an "open" category for them in some events as part of its new policy.

The new policy was passed with a roughly 71% majority after it was put to the members of 152 national federations with voting rights who had gathered for the congress at the Puskas Arena.

It will require transgender competitors to have completed their transition by the age of 12 in order to be able to compete in women's competitions.

A statement from FINA said that male-to-female transgender athletes will be eligible to compete only if "they can establish to FINA's comfortable satisfaction that they have not experienced any part of male puberty beyond Tanner Stage 2 (of puberty) or before age 12, whichever is later".

FINA President Husain Al-Musallam said: "We have to protect the rights of our athletes to compete, but we also have to protect competitive fairness at our events, especially the women's category at FINA competitions.

"FINA will always welcome every athlete. The creation of an open category will mean that everybody has the opportunity to compete at an elite level. This has not been done before, so FINA will need to lead the way. I want all athletes to feel included in being able to develop ideas during this process."

Transgender rights has become the subject of debate as sports seek to balance inclusivity while ensuring there is no unfair advantage.

The conversation around it intensified after University of Pennsylvania swimmer Lia Thomas became the first transgender NCAA champion in Division I history after winning the women's 500-yard freestyle earlier this year.

It followed New Zealand weightlifter Laurel Hubbard last year becoming the first transgender athlete to compete at the Olympic Games in Tokyo.

The new FINA policy also opens up eligibility to those who have "complete androgen insensitivity and therefore could not experience male puberty".

Athletes who have had "male puberty suppressed beginning at Tanner Stage 2 or before age 12, whichever is later, and they have since continuously maintained their testosterone levels in serum (or plasma) below 2.5 nmol/L." are also allowed to compete in women's races, FINA said.

It added that female-to-male transgender athletes (transgender men) are fully eligible to compete in men's swimming competitions.

Athlete Ally, an LGBTQ athletic advocacy group, responded to the announcement and said the eligibility criteria is "discriminatory".

They posted on Twitter: "[It] is discriminatory, harmful, unscientific and not in line with the 2021 IOC principles. If we truly want to protect women's sports, we must include all women."

But Sport Secretary Nadine Dorries has voiced support for FINA's move.

The Cabinet minister also stressed "it's important that those trans women who want to compete can compete" by having their own category.

When asked about Fina's decision on LBC, she said: "Yeah, I think it's absolutely the right decision that they've reached, and I am going to encourage other sports (to do the same).

"It is just unacceptable that trans women compete in women's sport."

And former British Olympic swimmer Sharron Davies tweeted her delight at the news.

She said: "I can't tell you how proud I am of my sport @fina & @fina_president for doing the science, asking the athletes/coaches and standing up for fair sport for females. Swimming will always welcome everyone no matter how you identify but fairness is the cornerstone of sport."

Back in May, International Olympic Committee president Thomas Bach said that sport cannot have a one-size-fits-all approach to transgender inclusion.

Controversies over the participation of transgender athletes in female categories have hit the headlines in cycling, swimming, weightlifting and other sports over the past year.

Olympic cycling champion Katie Archibald criticised the global governing body in her sport, the UCI, last month over its transgender policies, with trans athlete Emily Bridges ultimately excluded from the British Omnium Championships.

Lord Coe, the president of World Athletics, said the integrity of women's sport was "fragile" if federations did not get this right.

There have been calls to create an open category which transgender athletes could enter.

Mr Bach said the IOC has and will continue to assist sports in coming to "science-based decisions".

He told a press conference in May: "There is no one-size-fits-all solution. I think we all agree that this is about creating a fair competition. On the grassroots level, sport has to be inclusive, everybody has to have the access to sport.

"When it comes to competition as sport, we have to ensure fair competition. That means that you have to find out sport by sport, even discipline by discipline, where there is maybe an unfair advantage."