The number of civil partnerships registered in 2007 was half that of the previous year, new figures show.
The findings from the Local Government Association (LGA) were confirmed by the Office for National Statistics (ONS).
According to the ONS, 16,100 couples formed civil partnerships in 2006, the first full year in which they were legal. But in the first half of 2007, the last period for which ONS data is available, only 4,060 ceremonies were conducted.
In some areas the LGA figures suggested that a large proportion of couples applying to form civil partnerships changed their mind before the ceremony took place.
Wigan and Leigh Council said that only a third of the 94 ceremonies it received notice for actually went ahead in 2005/6.
Tony Grew, editor of the pinknews.co.uk website, said: “One reason for the decline may be that some gay people aren’t interested in formalising their relationship.
“Some don’t want to have all the formality of a civil partnership because they think it’s the death knell of a relationship.”
Ben Summerskill, head of homosexual lobby group Stonewall, claimed: “There was a big pent-up demand from couples in long-term relationships to form a civil partnership, which is why so many did it early on after the law changed in late 2005, so a tailing-off would be logical.”
Homosexual couples have been able to formalise a relationship through a civil partnership since December 2005.