More than a third of a million council and school support staff across England and Wales will start voting on Tuesday on whether to strike over pay.
Unison said an offer of a flat rate £1,925 was “nowhere near” enough to meet rising prices during the cost-of-living crisis.
The union, which had called for an increase of 2% above inflation, said that since 2010, the value of local government pay has fallen by 25%.
The six-week ballot, which closes in early July, includes refuse collectors, social workers, teaching assistants, librarians and others, working at 4,000 different employers.
A separate ballot for Northern Ireland will open in August.
Unison general secretary Christina McAnea said: “Too often council and school support staff are taken for granted. Without them, the services on which whole communities rely won’t exist.
