Britons may no longer be required to identify whether they are male or female on official census forms under recommendations made to officials.
A report suggested changes should be made to the official questionnaire after research found the question was discriminatory for trans or non-binary people - and was seen as "irrelevant and intrusive" by many respondents.
In future, it recommended the form's scope could be widened to take in more gender identities such as an "other" category or the question on sexual identity could be made optional.
The suggestions were made in a report carried out for the Office of National Statistics, which administrates the census in England and and Wales.
A census is held every ten years - with the last one in 2011 - and requires all households to fill out details about their households for official government records.
The report said: "We would tentatively recommend that an unchanged 2011 census question should not be mandatory, for the benefit of, particularly, intersex and non-binary people who cannot choose male or female as a reflection of their current sex or gender."
The authors also recommended changes "to better meet the needs of trans respondents", such as removing "sex" and adding one or more additional categories for non-binary and intersex people.
An ONS spokesman said the document is an update on research "on potentially collecting information on gender identity as well data on sex."
"It does not contain proposed census questions and suggests further research is required," he said in a statement.
"ONS has yet to formulate its recommendations for the 2021 Census. Once it has done so, the Government will bring forward a white paper which will include the census questions."