By the end of 2013 there were 2.6 million private sector employees in unions, a year-on-year increase of 61,000. It signals a continued reversal of a trend that saw numbers decline from 3.4 million in 1995 to 2.5 million in 2010.
The increase in numbers has largely been down to workers moving from public sector to private sector employment.
The three private sector industries that saw the largest rise in union membership are the arts and entertainment, financial and insurance, and transport and storage. In transport and storage, union membership reached 500,000 in 2013, up from 474,000 in 2012.
TUC national organiser Carl Roper told HR magazine industries with "solid frameworks" would always be more likely to attract union membership.
"Transport is traditionally an area with active unions who are well organised and have strong links with employers," he said. "It's a similar situation in the arts, which also has the professional element in union membership."
Roper added that union memberships traditionally fall during recessions, but the number of private sector workers looking to join unions at the start of the recovery is encouraging.
London Overground Rail Operations Limited (LOROL) HR director Darren Hockaday told HR magazine imminent changes to private railway companies is contributing to union membership.
"There's a desire to streamline the services provided in the area at the moment," he said. "People are concerned about potential job losses, which means people will be more inclined to be involved with the unions."
