Among the party’s manifesto policies released today is a pledge to add an “X” gender option to the passport.
The news will be welcomed by campaigners who have fought for people who do not identify as male or female to express their identity correctly on the document.
The new Lib Dem manifesto states in its equality section: “People should be able to go about their lives without fear of discrimination.
“However, hate crimes are on the rise and too many groups of people no longer feel safe.
“We believe that government needs to take an active role both in punishing discrimination and ensuring that it does not happen in the first place.”
The party has also pledged to reform the Gender Recognition Act to remove the requirement to provide reports from medical practitioners when applying for official recognition of a change in gender.
A Liberal Democrat government would also recognise nonbinary gender identities and “extend equality law to cover gender identity and expression”.
Last year, a campaigner lost a High Court bid to introduce gender-neutral “X” passports, claiming that not doing so breached human rights laws.
A judge ruled that it was not unlawful for Her Majesty's Passport Office to only issue male or female passports.
The campaigner, Christie Elan-Cane, tweeted on Tuesday that an appeal is due to get under way in two weeks’ time.
Last week the UK’s first publicly nonbinary candidate for Parliament told Yahoo News UK they believed there may have been past candidates who identified as nonbinary but had been unable to express that.
Pledges on Brexit, the economy and tax are also published in the Liberal Democrats’ manifesto.
“Our politics is in a state of flux, and this general election could lead to seismic change out of which a new and different politics can emerge,” leader Jo Swinson said, launching the policy pledges today.