More than 500 court workers in England and Wales will be elected to industrial action as of Monday over Covid security concerns.
Members of the Public and Commercial Services Union in 12 courts will vote in the coming weeks on whether to launch a campaign of action.
The union is calling for courts to be closed, with critical cases being handled virtually.
The union said courts should not reopen until an impact assessment has been carried out, staff are regularly tested and heightened security measures are in place.
Staff will be held at Birmingham Crown Court, Cardiff Crown Court, Highbury Magistrates Court, Isleworth Crown Court, Leeds Magistrates Court, Leicester Law Courts, Liverpool Law Courts, Manchester Crown Court, Snaresbrook Crown Court, elected at Southwark Crown Court and Wolverhampton Combined Court.
PCS General Secretary Mark Serwotka said: “The court staff have worked incredibly hard through this pandemic to keep the judicial system up and running, but they are deeply concerned for their safety.
“Management’s refusal to agree to our reasonable proposals, including the virtual execution of critical cases and mandatory Covid tests for employees, led to this vote.
“Strikes are always the last resort, but if our members vote to leave, we will support them all the way until we reach a just and safe solution.”
A Justice Department spokesman said: “During this pandemic, the government realized that justice must continue to be ensured for the public, victims and defendants.
“Every building we operate complies with government Covid safety guidelines, and public health experts have confirmed that our precautions remain sufficient to deal with the new strain of the virus.
“Positive test numbers agree with the wider community and it is likely that the vast majority infected the virus outside of court. It is simply wrong to claim that people are at increased risk of infection in court.”
Union members who are elected work as ushers and other support workers.