Unite is no longer Britain’s biggest trade union as Unison overtakes it on membership.

Official accounts published today show that Unite had 1,310,508 members by the end of 2017 – 66,498 less than Unison with 1,377,006 – losing its title as “Britain’s biggest union”.

Unite’s website claims it has 1.42 million members, but that figure has not been correct since 2012. Since then the union’s membership has been in steady decline, despite its absorption of over 50,000 members from construction union UCATT.

In that time Unite boss Len McCluskey has repeatedly claimed that his union’s membership was on the rise, making “winning and growing” the slogan of its July conference. He told the same conference that “we are nearly 90,000 members bigger” and wrote in 2013 that “Unite is a growing union with 3,000 new members in the last month alone”. Any new members entering the union appear to have been far outweighed by members quitting.

Unison’s rise to become Britain’s biggest union will be seen as an endorsement of its thoughtful and pragmatic approach to campaigning, in contrast to the bombastic protest politics of Unite. That approach has helped Unison lead the way on recruiting women and defeat the government on employment tribunal fees, a campaign that Unite had refused to take part in.

It will also call into question Unite’s outsize influence in the Labour Party. Unite alumnus Jennie Formby is now the party’s general secretary, handing the union four slots on Labour’s ruling NEC compared to Unison’s two.