A union last night warned of strike chaos hitting Scotland's biggest social work department from next week in a row about pay and job regrading involving 600 social care workers.

They will begin an indefinite work to rule from Monday after a ballot returned 97% of workers in support.

Social work staff and unions say a strike is inevitable because they claim David Comley, Glasgow council's director of social work, who is about to leave his £110,000-plus-a-year post, has threatened that anyone refusing tasks will be sent home, in breach of contract.

Last night union officials warned if anybody was suspended for a breach of contract, staff would walk out.

According to Unison, the public services union, the city council's workforce pay and benefits review has cut at least £1000 off social care workers' pay with some staff losing more than £5000.

The average social care worker, who would assess and support care packages, currently gets paid between £18,000 to £25,000. If care workers strike, union leaders believe the vast majority of the 5000 people who work in Glasgow City Council's social work department will support their action and will not cross any picket line.

Services would be affected across the board from child abuse inquiries, helping the elderly and those with mental health problems to court support which would be hit hard by any lengthy stoppage.

Brian Smith, secretary of the Unison's Scottish social work stewards committee said: "Industrial action is chaotic, that is the nature of the beast. As far as we are concerned the council could easily provoke a strike.

"We feel the council can sort this out by implementing the job evaluation scheme properly. They should value the job of the social care workers to the level that they should be valued at and pay the appropriate wage."

Glasgow City Council accused the union of adopting a "cruel and cynical tactic" which would hurt the most vulnerable in society.

Last night a spokesman said the action was premature as the appeals process has not been exhausted. The council admits that one in three of the social care workers will lose out through the regrading.

"It is clear the unions have adopted a strategy of trying to force the council's hand by hurting the most vulnerable in society," said a spokesman.

"It is a cruel and cynical tactic and Glaswegians would not expect us to give in to it.

"The majority of people who are threatening action have lost no money under the review and we are committed to ensuring that those who are in detriment will have incomes protected in the long term."

If the council were to meet the union demands an extra £3m would have to be found to pay each social care worker, typically £5000 a year extra annually, he said.

The move comes days after a nine-month investigation by the Social Work Inspection Agency (SWIA) into Glasgow City Council called on staff to move more quickly to ensure the long-term future of children in its care and clear the backlog of offenders requiring case workers.

The dispute has been sparked by the city council's attempt to regrade social care workers, providing them with new role profiles' or job descriptions, prompted by the legacy of an equal pay ruling which requires them to harmonise the wages of male and female workers.