Fina, swimming's world governing body, has voted to stop transgender athletes from competing in women's elite races if they have gone through any part of the process of male puberty.

Fina will also aim to establish an 'open' category at competitions for swimmers whose gender identity is different than their birth sex.

The new policy, which was passed with 71% of the vote from 152 Fina members, was described as "only a first step towards full inclusion" for transgender athletes.

The 34-page policy document says that male-to-female transgender athletes are still eligible to compete in the women's category "provided they have not experienced any part of male puberty beyond Tanner Stage 2 [which marks the start of physical development], or before age 12, whichever is later".

The decision was made during an extraordinary general congress at the ongoing World Championships in Budapest.

It means that transgender American college swimmer Lia Thomas, who has expressed a desire to compete for a place at the Olympics, would be blocked from participating in the female category.