Parking wardens in Wiltshire are set to strike as part of an ongoing row over pay.
GMB union members are due to walk out for a week on Saturday 10 December which will take in two of the busiest shopping Saturdays in the run-up to Christmas.
The union has warned a seven-day strike could see the council lose up to £200,000 in lost parking charges and fines.
The dispute is over the rate staff are paid for working unsociable hours, undertaking standby duties and call-outs.
The union says the proposals would result in traffic wardens losing around £2,000 per year, with social workers losing up to 20 per cent of their pay, or £3,500 annually.
Current workers say they do not want their pay reduced but argue that new recruits could be brought in at a lower rate.
The council says it is necessary to change the pay plan for everyone to ensure that services are delivered in a 'financially viable' way.
The GMB union previously called off a week-long strike at the beginning of July after talks over protecting workers' pay but now claims the council has gone back on its promise.
Keith Roberts, GMB regional organiser, said: “We thought that a deal had been reached with the council, and called off a strike in the summer because the council agreed for pay protection for the lifetime of the contracts of existing staff, which guaranteed that they would lose no money.
“In the current cost of living crisis, actually taking money away from staff is crazy, and even the suggestion of a future pay cut has caused a crisis of retention and recruitment."
However, the council say this is not true and they are 'frustrated' with the union's decision.
Terence Herbert, Wiltshire Council Chief Executive, said their offer "would have seen four years of pay protection for current staff until 2027, which is a far more generous offer than we have seen any other local authority put forward, particularly given the current financial climate.
“Lifetime protection was never agreed, despite what GMB claim.
“If members of the civil enforcement team do go on strike then we will have a contingency plan in place – people will still be required to pay for the use of our car parks.
“Unfortunately throughout this ongoing process GMB has regularly said one thing to us and then something completely different publicly, and this disingenuous behaviour has been incredibly frustrating."