Winchester and Southampton Crown Courts, as well as the city’s magistrates’ courts, are expected to remain open although cases could be disrupted.

The National Association of Probation Officers (NAPO) said its staff working in the courts, HMP Winchester and HMP Isle of Wight and in the community would all be taking part in the walkout.

Eight out of ten of the 3,600 NAPO members around the country voted to strike.

A spokesman for the National Offender Management Service said: “The National Offender Management Service has wellestablished contingency arrangements for handling major incidents, including episodes of industrial action.

“We will be monitoring closely the impact that the strike action has on the prison estate. However, at this stage we do not anticipate that this will have a major impact on prisons.”

Guards from the Prison Officers’ Association will join rallies and demonstrations outside the prisons outside working hours but are banned by law from striking.

A spokesman for Her Majesty’s Courts and Tribunals Service said its top priority was to ensure public safety.

“We have robust contingency plans in place which will prioritise the delivery of our most essential services. These include custody cases and urgent family cases.

“Our aim is to keep disruption to a minimum. Our intention is to continue to work with all staff to deliver our services to the public.”