Keir Greenaway, GMB Scotland’s senior organiser, said the cost-of-living crisis would become a “catastrophe” unless the Scottish Government takes action.
It came as Cosla, the body that represents Scotland’s councils, held talks with Deputy First Minister John Swinney and other Scottish ministers on Wednesday afternoon in a bid to avoid crippling strikes.
No immediate outcome appeared to come out of the talks, with a Cosla leaders’ meeting expected to take place on Friday.
Mr Swinney said in a statement: “Although the Scottish Government has no formal role in the national pay negotiations for local government workers, we are working jointly with Cosla to explore all options available and held constructive discussions today with council leaders.
“Local government workers play a crucial role in our communities and are integral to our recovery from the pandemic. I would urge all parties to continue a dialogue and reach a resolution which avoids industrial action.”
Local government workers have voted to reject a 2 per cent pay offer from Cosla, which says it is unable to offer more without extra funding from the Government.
Union leaders say they have “legal mandates to disrupt the operation of over 1,200 schools across 16 local authorities in Scotland” as well as waste and recycling services in 25 councils.
The GMB urged the Scottish Government to take more responsibility for the ongoing pay row.
Mr Greenaway said: “Tens of thousands of local government workers are at real risk of falling into working poverty this winter unless a significantly improved pay offer that confronts this cost-of-living crisis is tabled for their consultation – that’s the warning we are sending to political leaders.
“Despite the Deputy First Minister’s plea to the UK Government for more money, the Scottish Government have been content to play politics before when it comes to finding additional support for other areas of our public services, so they can’t divert from the responsibilities they do have.
“The truth is that our political leaders have been sleeping at the wheel on the pay offer for local government because the paltry 2 per cent offer, worth less than a tenner a week extra for the lowest paid, was overwhelmingly rejected by staff in March.
“They have already left these key workers at the mercy of soaring inflation and eye-watering energy bills for nearly six months, and as we head into a grim winter where these pressures will only rise further, this crisis will become a catastrophe for our members unless the government acts now.”
It is estimated more than half of Scotland’s 250,000 council workers earn less than £25,000 a year.
With the prospect of industrial action closing schools and seeing rubbish go uncollected, Mr Greenaway said this could be avoided if a “significantly improved offer is put to our members”.
He said: “For me, the Scottish Government has got the ability, has got some levers to raise income for itself to be able to give to public services and it is not taking those options.”
The trade union leader added: “It is up to the Scottish Government to come on and think of some of those solutions.”
Pay settlements for council workers – apart from teachers – are the responsibility of Cosla and are determined through negotiations at the Scottish Joint Committee, but the Scottish Government has been urged to do more.
In a letter sent to Chancellor Nadhim Zahawi over the weekend, Mr Swinney said last year’s UK Spending Review, which determined the majority of the Scottish Budget, “did not take into account the level of pay increase recently proposed by the independent pay review bodies”.
But the Scottish Tories have accused the SNP of trying to “shift the blame” onto the UK Government.