Urgent talks are expected to be held after unions representing school support staff, including teaching assistants, rejected a 1.5 per cent pay offer.

Unison, Unite and the GMB unions have all dismissed the offer as “insulting”, saying it fell well short of the 10 per cent claim submitted earlier this year.

Employers, who negotiate pay on behalf of local authorities in England, Wales and Northern Ireland, said the offer would cost £279 million, affecting 1.5 million workers, ranging from architects and social workers to school support staff and refuse collectors.

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Unison’s head of education, Jon Richards, said: “This offer simply isn’t good enough. Council and school staff have done so much this past year. They’re understandably feeling more than taken for granted. It’s insulting.

“Negotiations with the employers are now essential if council and school staff are to get a better deal.

“More resources from Westminster would help relieve the financial pressure on councils and schools, and fund a more substantial increase for staff.”

Unite national officer Jim Kennedy said: “We mistakenly believed that, after the last year, where local government workers have supported, protected and sustained our communities, that the employers would finally offer a fair pay increase.

“Local government workers are increasingly voting with their feet and leaving the sector. This trickle of resignations will turn into a torrent unless low pay is addressed.”

Rehana Azam, GMB national officer, said: “GMB rejected the poor offer and have now been asked by senior reps to seek urgent talks with the employers to assess if there is scope for proper negotiations.”