The Ministry of Justice has warned that it will take legal action over "unlawful" industrial action by prison staff.
Officers at jails in England and Wales are threatening to withdraw labour in a dispute about pay and pensions.
From Wednesday (March 1) members of the Prison Officers Association (POA) are set to withdraw from voluntary duties, which include providing first aid and negotiating hostage situations.
Manning of Tornado teams which are deployed during disorder is also among the voluntary roles which will be affected by the action.
The Ministry of Justice said it had previously struck a deal with the union's leadership and would now seek to block action in the courts.
A spokesman said: "Industrial action by prison officers is unlawful. If the POA do not withdraw their bulletin, we will seek an injunction to prevent any such action occurring.
"We made a good offer to the Prison Officers Association in December, which was endorsed by their leadership but rejected by the POA membership."
But the union has said in a briefing paper: "The POA condemns the systematic failure of Noms (National Offender Management Service) to provide safe, decent and secure prisons, failures which have created a prison service in crisis.
"More and more members are being assaulted every day, the increase in self-inflicted deaths and daily security breaches are unacceptable and as a result of staff shortfalls and budget cuts."