Trade union membership increased by almost 90,000 last year to 6.4 million amid the biggest outbreak of industrial action for decades, new figures show.

The proportion of employees who were trade union members increased to 22.4% in 2023 – up from 22.2% in 2022, according to official figures.

The number of male employees who were union members increased by 172,000 to around 2.9 million, while the number of women in a union fell by 83,000 on the year to 3.5 million.

Union members in the private sector increased by 100,000 on the year to 2.5 million, and there was a 12,000 fall in trade union membership among public sector employees to 3.8 million.

TUC general secretary Paul Nowak said:  “This increase in trade union membership is welcome, but our movement is not complacent.

“We need to get more people into trade unions – especially younger workers.

“Being a member of a union gives you an independent voice at work and remains the best way to win better pay and conditions.

“Every day unions reach agreements with employers that protect and enhance members’ jobs and livelihoods and keep workplaces safer.”

Mr Nowak added that employment law remained “stacked against” unions and workers, saying Labour’s New Deal for Working People would allow unions to reach more workplaces and help drive up pay and conditions.