There were 232,000 same-sex couples living together last year, up from 152,000 in 2015, the Office for National Statistics (ONS) said.
The biggest rise has been among married couples, who accounted for almost 30% of all same-sex couples living together in 2018, compared with less than 10% in 2015.
Same-sex marriages have been legal since 2014. Civil partnerships for same-sex couples – which grant similar rights and responsibilities to a marriage – have been legal since 2005.
The ONS said one in five same-sex families included civil partners, down from nearly a third. It defines a family as a couple with or without children, or a lone parent with at least one child, who live at the same address.
Sophie Sanders, ONS head of demographic analysis, said the introduction of same-sex marriage was a big contributor to the overall increase in same-sex couples living together.
“We’re also generally seeing increasing acceptance of same-sex relationships so people may feel more comfortable to say they are living together,” she told the Thomson Reuters Foundation.
Sanders said the trends for same-sex and heterosexual couple families were going in opposite directions, with the latter increasingly choosing cohabitation and marriage falling in popularity.
-Emma Batha @emmabatha – Thomson Reuters Foundation