A 23-year-old woman who was given “experimental” puberty-blocking drugs at 16-years of age is taking legal action against the UK’s first gender clinic for children.

Keira Bell said her gender reassignment treatment, which she now “very seriously regrets”, quickly “snowballed” after she was referred to the clinic by her GP.

The teenager began taking the life-altering treatment after three one-hour long appointments at the Tavistock and Portman NHS Trust clinic.

Ms Bell said, at the time, she was unaware of the real consequences of taking the hormone blockers, which were prescribed by the clinic to halt the development of her female body.

According to ITV News, Ms Bell said the treatment made her voice drop and caused her to grow facial hair. She went on to have chest surgery and a double mastectomy through the adult clinic, which she said took place after just two appointments.

In the landmark case, the judge, Mr Justice Supperstone, granted permission for the trial to go ahead, saying it was “plainly arguable” the clinic was acting unlawfully in giving children puberty blockers, The Sunday Times reports.

Ms Bell said she is involved in the case “because I do not believe that children and young people can consent to the use of powerful and experimental hormone drugs like I did.”

“I think talking therapies when you’re under-18 are always going to be more beneficial than immediately putting yourself on life-altering drugs that are going to affect the rest of your life and I wish that’s what I had for example,” she said.

Ms Bell went on to say, “At the time, I thought it was the best decision I was making, it’s a time will tell sort of situation because nothing else will indicate whether you will stay on that pathway for the rest of your life or not.”

In an interview with BBC News, Bell said, “When you are that young, you don’t really want to listen to anyone, and a lot of things won’t get through. So, I think it’s up to these institutions, like Tavistock, to step in and make children reconsider what they’re saying. Because it is a life-altering path that you’re going down, and it’s not guaranteed to work.”

Last year a former transgender male in the UK established a charity group to support “hundreds” of young transgender people seeking help in returning to their biological sex.

Charlie Evans, founder of The Detransition Advocacy Network, told Sky News that since she decided to stop transitioning, she has been contacted by “hundreds” of people who regret transitioning, some of whom have had full gender reassignment surgery.

“I’m in communication with 19 and 20-year-olds who have had full gender reassignment surgery who wish they hadn’t, and their dysphoria hasn’t been relieved, they don’t feel better for it,” she said.

In the UK, puberty blockers can be prescribed to any child suffering from gender dysphoria from age 10 by the NHS’s Gender Identity Development Service (GIDS). So far, GIDS has treated approximately 230 children under the age of 14 with puberty blockers.

Although the clinic has insisted that such treatments are safe and reversible, GIDS have been accused of hiding bad results about its use of the experimental puberty blockers on teenagers.