Cycling's world governing body the UCI will ban female transgender athletes who transitioned after male puberty from participating in women's events on its calendar under new rules which come into force from Monday.
Under the existing regulations, transgender women can compete in the female category providing they have a maximum permitted plasma testosterone level of 2.5 nanomoles per litre.
In May, the UCI defended that policy as being "based on the latest scientific knowledge" following controversy after American Austin Killips won the Tour of the Gila in New Mexico to become the first transgender woman to win a UCI women's stage race.
But the governing body announced on Friday that its management committee had voted to change the rules after further consultation with stakeholders and a review of scientific, legal and human rights considerations.
A statement said that review had concluded that the maximum permitted testosterone level previously used was not "sufficient to completely eliminate the benefits of testosterone during puberty in men".
The statement added: "Given the current state of scientific knowledge, it is also impossible to rule out the possibility that biomechanical factors such as the shape and arrangement of the bones in their limbs may constitute a lasting advantage for female transgender athletes."
UCI president David Lappartient said: "First of all, the UCI would like to reaffirm that cycling - as a competitive sport, leisure activity or means of transport - is open to everyone, including transgender people, whom we encourage like everyone else to take part in our sport.
"I would also like to reaffirm that the UCI fully respects and supports the right of individuals to choose the sex that corresponds to their gender identity, whatever sex they were assigned at birth.
"However, it has a duty to guarantee, above all, equal opportunities for all competitors in cycling competitions.
"It is this imperative that led the UCI to conclude that, given the current state of scientific knowledge does not guarantee such equality of opportunity between transgender female athletes and cisgender female participants, it was not possible, as a precautionary measure, to authorise the former to race in the female categories."
In May, British Cycling introduced its own new policy .
The policy created an 'open' category in which transgender women, transgender men, non-binary individuals and those whose sex was assigned male at birth are eligible to compete, with the 'female' category reserved for those assigned female at birth and transgender men yet to begin hormone therapy.
British transgender cyclist Emily Bridges, who spoke out strongly against British Cycling's new policy, responded to the UCI's announcement by saying the governing body was "regressing from any commitment to diversity or progress".
"I accepted a few weeks back that I had to completely separate my self-worth from cycling and move on if I was to ever actually become a functioning individual and doing this has helped to lessen the blow of this," Bridges said in a statement posted on social media.
"I haven't given up though. I will not allow myself to give up on the other athletes I fight for."
