Social care workers who are employed by Scotland's biggest local authority are to stage an indefinite walkout in a dispute over pay and regrading, it emerged yesterday.

The 600 staff, frustrated at Glasgow City Council forcing them to postpone plans to begin a work-to-rule in protest over job regrading from last Monday, carried the strike vote overwhelmingly at a meeting of more than 700 care staff, social workers and team leaders.

Some 97% of those balloted supported an indefinite work-to-rule from Monday and 88% backed strike action.

A further strike ballot is to be conducted among more than 1000 social workers, practice team leaders and other ancillary care staff are to be balloted over supporting the care workers.

Union leaders said that, in a show of hands, only a handful of those at yesterday's meeting voted against an all-out strike.

The union say the stoppage, due to start on July 23, would cause "chaos" and would affect services across the board, including child abuse inquiries, care for the elderly, mental-health support work, court support and drug addiction work.

Unison, the public-services union, says the council's workforce pay and benefits review has cut at least £1000 off social care workers' average pay of about £21,000, with some staff losing more than £5000.

It said new grades, assigned last autumn, fail to take account of all the work the assistants were expected to do.

The council has accused the union of adopting a "cruel and cynical tactic" which would hurt the most vulnerable.

Union leaders believe the vast majority of the 5000 people who work in Glasgow City Council's social work department will support the care workers in their action and will not cross any picket line.

Unison claims the council was threatening court action to challenge the legality of the work-to-rule, a claim denied by the council, meaning any staff who take action could be putting their jobs on the line.

Mike Kirby, Glasgow branch chairman of Unison, said: "The council has boxed us into a strike situation rather than a work-to-rule. It would cause a lot of disruption.

"We thought we could take a work-to-rule which would have been backed up with strike action if the council chose to take disciplinary action against anyone. But legal constraints have meant we have had to move to wider-scale action."

The union says the work-to-rule had been devised to allow staff to protest while trying to avoid depriving vulnerable children and adults of services.

Social work staff and unions say David Comeley, the city council's director of social work, who is about to leave his £110,000-plus-a-year post, threatened that anyone refusing tasks in a work-to-rule would be sent home, in breach of contract.

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

It also found staff had little confidence politicians valued their work or that senior managers offered effective leadership.

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

Glasgow City Council says the action is premature as the appeals process has not been exhausted. It admits one in three social care workers will lose out through the regrading.

The council has said that if it were to meet the union demands, it would cost £3m to pay each social care worker typically £5000 a year extra.