More than 43,000 council workers in waste and recycling, schools and social care are to be balloted for strike action.
Staff are frustrated that they should have been given their annual pay rise at the start of April and have only received an offer of just 2% or 39 pence per hour, the unions says.
UNISON had hoped an improved formal pay offer would be forthcoming by this week, to avoid the the long delays employees experienced last year.
The ballot will be in three phases, with waste and recycling staff being balloted first in the coming days, with others to get their ballot papers later in the summer.
If refuse workers vote in favour of a strike, action could start in July, meaning rubbish would start piling up in the streets.
UNISON Scotland local government committee chair Colette Hunter said: “Council staff should have received a cost of living pay rise last month. But the offer is miles away from the level staff deserve.
“There seems no other option but to begin strike ballots. Workers aren’t willing to put up with long delays.
“Council waste and recycling staff will receive official strike ballots through the post very soon. Unless Cosla comes up with a fair pay offer it looks like strikes will be going ahead.”
UNISON Scotland lead for local government David O’Connor said: “The employers promised an improved offer would come this week. Council staff have made it very clear that they’re not willing to be strung along.
“If Cosla makes a better proposal soon, it’ll be considered. Strike action is always the last resort, but as it stands, there’s no choice but to start an official ballot.”