UK residents should be able to identify as non-binary rather than male or female on their passports, LGBT campaigners say.
Stonewall claims being able to put an "X" on their passport would help transgender people and those who do not identify with a single gender deal with face difficulties at passport control.
The recommendation is one of a series of changes recommended by the Stonewall Trans Advisory Group, as part of a five-year plan to create equality for trans people.
Tara Stone, a member of the group, told BBC Radio 4's Today programme: "For trans people who identify as non-binary, that is neither male or female or some combination thereof, it would give them an option that wasn't prescriptive, whereas the only options at the moment are prescriptive for them.
"It basically allows them to express their identity."
Around 650,000 people identify themselves as trans across the UK.
The measure has already been introduced in Australia and Ireland.
Other recommendations in the report include revising the Gender Recognition Act so people would not need medical evidence to get their gender recognised by law.
Further changes would reform the Equality Act to include "gender identity" as a protected characteristic, as well as removing the terms "gender reassignment" and "transsexual".
The proposed changes come after reports Britain would bring back its old blue passports once Article 50 is triggered.
Additional reporting by the Press Association.
