Unions representing millions of British public sector workers have announced plans to hold strike ballots that could lead to a series of one-day national work stoppages later this year.

At issue is the government’s failure to negotiate higher contributions to public sector pensions that are acceptable to the unions. The unions are upset with budget reforms that could raise the retirement age and increase employee pension contributions. Government ministers say the pensions are no longer affordable, with more people living longer and driving pension costs higher.

The biggest public sector union, Unison, says its 1.1 million members will put the strike action to a vote. The workers are employed by 9,000 different companies ranging from local government to health care, schools and higher education, police, the voluntary sector and the environment.

The Fire Brigades Union that represents firefighters also has announced plans for a strike vote.

The unions have continued negotiating up to this point, but they have accused the government of being inflexible by presenting an offer and refusing to modify it.