A campaigner has been granted permission to bring a High Court challenge against the Home Office over gender-neutral passports.
Christie Elan-Cane, 60, believes the current UK passport application process is insufficient, as it does not cater for those who identify as neither male nor female.
Elan-Cane's lawyers appeared at the Royal Courts of Justice in London on Wednesday (11 October) where they were told their judicial review for a third "x" option on travel documents could proceed to a full hearing.
Granting the petition, Mr Justice Gilbert said: "I am satisfied this case passes the test for the grant of permission, and is arguable."
The case will be heard on a date yet to be fixed.
Elan-Cane, who was born female but identifies as "non-gender", appeared before the Commons women and equalities select committee two years ago to give evidence on transgender equality.
"Legitimate identity is a fundamental human right but non-gendered people are often treated as though we have no rights," Elan-Cane said. "The UK's passport application process requires applicants to declare whether they are male or female. It is inappropriate and wrong that someone who defines as neither should be forced to make that declaration.''
Elan-Cane argues the government is discriminating against its own citizens because it already allows those identifying as gender neutral on foreign passports to enter the country. Lawyers will argue the current rules breach the European Convention on Human Rights.
The push for a judicial review comes after Canada last month became the 10th country to offer citizens the "x" gender option on travel documents. Ireland, Australia, Denmark, Germany, Malta, New Zealand, Pakistan and India had already done so.
Since July, more than 40 MPs have signed an early day motion in favour of gender-neutral passports.
The proposal has also been backed by Stonewall, a leading LGBT rights group.
"Not having legal recognition means non-binary people must constantly live as someone they are not," the charity said back in April.
Earlier this week, it emerged the Office for National Statistics (ONS) was in talks to have the question of gender made optional on the next national census in 2021.
The move, said to prevent discrimination against transgender people, would make the UK one of the first countries in the world not to require its citizens to tell officials what sex they are.
Elan-Cane was one of 14 experts who advised the ONS at a "gender identity workshop" in August 2016, The Sun reported.