The UK's first openly transgender judge is planning a challenge to the Supreme Court's ruling on biological sex in the European Court of Human Rights.
Dr Victoria McCloud suggested that the UK Supreme Court judgement and new equality watchdog guidance, which is being implemented by Government bodies including the NHS, violated her human rights.
Earlier this month British judges ruled that the terms “woman” and “sex” in the Equality Act only refer to a biological woman and to biological sex. It means that trans women and men could be made to use single sex spaces that correspond with the gender they were assigned at birth.
Dr McCloud, who stepped down as a judge last year, argued that the court had failed to consider human rights arguments put by transgender people.
She said she felt "contained and segregated" by the ruling and the legal "nonsense" left her being "two sexes at once".
The 55-year-old was one of at least two trans people who had asked to present arguments to the Supreme Court about how its outcome would affect the trans community.
However, the interventions from individual activists were rejected and the Supreme Court instead considered arguments on trans issues from the human rights campaign group Amnesty International.
Dr McCloud, who came out as trans in her twenties and has legally changed the sex on their birth certificate, told the BBC: "Trans people were wholly excluded from this court case. I applied to be heard. Two of us did. We were refused.
"[The court] heard no material going to the question of the proportionality and the impact on trans people. It didn't hear evidence from us.
"The Supreme Court failed in my view, adequately, to think about human rights points."
Dr McCloud has a Gender Recognition Certificate, which means her birth certificate now states that she is female. But the Supreme Court ruling means she is defined as a man for the purposes of the Equality Act.
She added that her and other campaigners plan to go to the European Court of Human Rights (ECHR) in Strasbourg to seek a declaration that the actions of the UK government and Supreme Court judgement have violated “fundamental human rights".
"Just as the prime minister didn't know what a woman was, actually the Supreme Court don't know because they haven't defined biological sex," she said.
"The answer is that a woman in law is someone with the letter F on her birth certificate."
Dr McCloud was a High Court Master, but stood down a year ago saying she could not continue during an increasingly difficult public debate that had led to her being singled out for abuse because of her gender identity.
Announcing the Supreme Court ruling earlier this month, Lord Hodge said: "The unanimous decision of this court is that the terms woman and sex in the Equality Act 2010 refer to a biological woman and biological sex.
"But we counsel against reading this judgement as a triumph of one or more groups in our society at the expense of another, it is not."
Maya Forstater, of campaign group Sex Matters, which was part of the case, said: "McCloud may wish to undertake this challenge as a personal pursuit, but... any chance of success lies more in the realm of fantasy rather than reality.
"The Supreme Court has just laid out in a clear and unanimous decision precisely how the Equality Act has to be interpreted, and one of the guiding principles of this exercise in statutory interpretation was to ensure that the Equality Act was compatible with the Human Rights Act."
