COURT staff in Worcestershire may strike in protest at being made to work in new buildings.
Three-quarters of court staff are to be transferred. Those at Droitwich at the moment will relocate to Worcester in the autumn when the new Castle Street court opens.
Staff now based at Redditch will work at Kidderminster from July.
Both new courts are to be run by Rentokil Initial Management Services.
The Association of Magisterial Officers fears some workers will quit their jobs unless relocation costs are guaranteed.
"Our members are not traditionally militant, but can't accept the current management offer," said AMO general secretary, Rose Eagleson.
"All our members who transfer to RIMS or who relocate deserve to be treated fairly."
Some staff, such as cleaners, caretakers and receptionists, will transfer to work for RIMS.
Most employees will continue working for the court service.
The AMO said it had balloted its members in Worcestershire because talks with the West Mercia Magistrates' Courts Committee over terms for redundancy and relocation for affected staff had faltered.
The union, which represents staff such as court clerks, alleged the current management offer was "significantly less than the norm for the public sector".
The union hopes the results of the vote, which will be supervised by independent figures in London, will be known by next Tuesday.
But the MCC's chief executive, Nick Jones, disputed the claims.
He said the service had pledged to abide by nationally-agreed conditions of service, such as relocation costs.
"I can't comment on what will happen if the union decides to go on strike," Mr Jones said.
"We'll cross that bridge when we come to it."
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