Council workers could take part in strike action that would "close schools across the country and see waste piling up on the streets" without an improved pay offer, the First Minister has been warned.
Leaders of Unison, Unite and GMB unions have written to Nicola Sturgeon and Finance Secretary Kate Forbes calling for talks on local government pay to take place as a "matter of urgency".
The unions said the 2% that has been offered to council workers is "derisory".
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Trade union leaders have served notice to local authorities across Scotland, advising them of their intention to ballot for industrial action among those working in schools, early years centres and waste and recycling services.
With members having voted "overwhelmingly" in favour of action in consultative ballots earlier this year, the unions wrote: "Be in no doubt about the strength of feeling that exists amongst our membership and the consequences of these statutory ballots being successful - it would close schools across the country and see waste piling up on the streets."
Unite general secretary Sharon Graham said that the Scottish Government and leaders in the Convention of Scottish Local Authorities were "now facing widespread strike action which will be entirely of their own making".
Ms Graham said: "They need to act on the desperate levels of local government pay for most workers.
"A 2% pay offer when the broader cost of living is now above 11% is a punishing real-terms pay cut. This is not debatable - it's a fact.
"Our members are determined to secure fair pay and they have their union's full support in this fight for better jobs, pay and conditions in local government."
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Wendy Dunsmore, Unite industrial officer, said local government had been "the biggest loser" in the Scottish Government's recent spending review, with councils seeing "funding frozen for the rest of the parliament".
But she added: "You can't deliver first-class public services through pathetic pay offers and major cuts to funding for local services. It's simply impossible.
"The Scottish Government and Cosla need to move significantly from the 2% offer, and let's not forget that there's been a willingness to do this in other areas of the public sector."
The GMB union is also balloting 10,000 of their members working in waste and cleansing, schools and early years services, on action.
Keir Greenaway, GMB Scotland senior organiser, said the current offer amounted to a rise of less than £10 a week for staff earning less than £25,000 per year.
That ballot begins on Monday and runs until July 29, and comes after the Scottish Government's spending review which forecasted a real-terms cut in local authority funding.
Mr Greenaway said: "Council workers and the vital services they deliver are firmly in the sights of Kate Forbes' cuts agenda, and if left unchallenged the lowest paid will pay the price in the biggest cost-of-living crisis for 40 years.
"This is what years of failure at all levels of government looks like - a decade of failed austerity, the passing on of cuts to communities, and a meek acceptance of the consequences locally.
"It's a far cry from the doorstep applause of virtue-signalling political leaders just two years ago.
"It shows everyone there are no political superheroes and if you want wages that confront soaring inflation then you need to organise and fight for it.
"That's exactly what our members are doing and unless an improved pay offer is tabled then industrial action looks inevitable."
A Cosla spokesman said: "Cosla values the essential roles that all local government workers carry out on a daily basis. We remain in active discussions with our trade union partners."
