Unite criticised the revised offer from the Convention of Scottish Local Authorities (COSLA) which it said would represent an increase of only £0.01 per hour for those on the lowest pay, effective from January next year.

It warned members across 11 councils will walk out later this month unless something "dramatic" happens over the coming weeks.

It comes after the Unison and GMB Scotland unions also rejected the two-part offer that COSLA had said would provide at least a £1,929 increase in annual salary for workers by 1 January 2024.

School support staff including cleaners, caterers, janitors and school support assistants will take part in the coordinated action over three days from Tuesday 26 September to Thursday 28 September.

Unite general secretary Sharon Graham said: "It has taken COSLA five months to increase their offer by a measly 38p a week for the lowest paid council workers.

"Unite's local government representatives rightly rejected this offer.

"The fight for better jobs, pay and conditions in local government goes on, and if needs be by strike action. Unite will back its members all the way."

The trade union has urged First Minister Humza Yousaf to directly intervene in the pay dispute.

Unison has warned that more than three-quarters of Scotland's schools could shut during the strike action.

It has mandates in 24 local authority areas across Scotland while GMB Scotland members plan to walk out in 10 council areas.

COSLA said the offer would mean the lowest paid workers would see a 21% increase in their pay over a two-year period.

It said the pay offer currently on the table will cost councils just under half a billion pounds and said that council leaders had gone to the "absolute limits of what local government can afford".

Read more:
New train drivers' strike announced
Coordinated strike action against three major carmakers

Commenting after Unison and GMB Scotland rejected the offer on Thursday, COSLA resource spokeswoman Katie Hagmann said: "I am doubly disappointed today, firstly with the rejection itself, but perhaps more importantly with the fact that they did not take the revised offer to their membership for consideration."

She added: "It must be remembered that we are talking about a pay package worth over £440m, specifically targeted at the lower end of our workforce.

"A pay package which not only compares well to other sectors but recognises the cost-of-living pressures on our workforce and which would mean the lowest paid would see a 21% increase in their pay over a two-year period.

"Whichever way you cut it, this is a very strong offer in the financial climate we find ourselves. We have a duty to ensure that services are sustainable within the funding for pay we have available."