Union bosses have warned they are moving “full steam ahead” for a possible summer strike as they rejected a “derisory” pay offer made to council workers across Scotland.

Unite said on Friday it had “rejected outright” the deal put on the table by local government body Cosla.

The proposed 18-month deal would give council staff a 2.2% uplift from April this year, with a further 2% hike in October.

Cosla said it is a “strong, fair and credible” offer, adding it is at the “limit” of what councils can afford.

Unite confirmed it is pressing ahead with plans to ballot key groups of its local government membership for industrial action – with further details to be announced next week.

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The union warned of the prospect of industrial action this summer, as general secretary Sharon Graham slammed the offer made by council employers.

Ms Graham said: “Cosla has taken months to put a formal pay offer to our local government membership, and it’s a derisory one at that.

“Unite’s representatives rightly rejected this offer outright. The fight for better jobs, pay and conditions in local government will continue.

“We are clear that our members shouldn’t settle for anything that doesn’t come close to meeting their demands.”

Graham McNab, Unite industrial officer, warned: “Unite is moving full steam ahead towards industrial action this summer unless Cosla makes a significantly improved pay offer.

“The pay offer doesn’t come close to meeting the aspirations of our members in local government.”

Cosla has stressed the pay deal on the table is “at the limit of affordability, given the severe financial constraints councils are facing in the context of a flat-cash local government settlement”.

A spokesperson for the local government body said: “We believe that this is a strong, fair and credible offer which reflects the high value council leaders place on the local government workforce and the invaluable work they do every day to serve our communities.”

Unison, the largest local government union in Scotland, said on Thursday that the offer “falls short of the level local government workers deserve”.

It said it is recommending staff vote to reject the pay deal.

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Leaders of GMB Scotland, meanwhile, said their local government committee rejected the offer at a meeting on Friday.

Its members have already backed strike action in a consultative ballot, if no acceptable pay offer was made, with a formal ballot of care workers currently taking place.

Keir Greenaway, GMB Scotland senior organiser, said the pay offer from Cosla is “too late and too low”.

Mr Greenaway added: “The delay was unacceptable and the offer is unacceptable.

“It means council workers in Scotland being offered less than colleagues in England and Wales and it raises grave concerns about councils’ promise to pay all workers £15 an hour by 2026.

“This offer comes nowhere close to matching that commitment.

“We do not need any more empty promises and excuses. We need a pay offer that fairly reflects the crucial work being done by our members in local authorities delivering the frontline services that Scotland is built on.”