Steve Baines, branch secretary of the prison officer's association, said a walk-out would cause maximum disruption after the national union rejected a "derisory" 1.6% pay rise. If a walk-out went ahead, it is expected police and army officers would be drafted in to control security at Britain's prisons, including Walton, which has 1,400 inmates.

It is likely many prisoners could be left to spend the 24 hours locked in their cells.

Mr Baines said: "We want a sensible solution. But this was a derisory pay offer, when you consider that the Prison Service has been one of the most successful services, meeting 15 of its 18 targets this year.

"It is an insult to offer 1.6% when other public services have received awards of 3%."

The last industrial action at Walton was a one-hour stoppage, seven years ago, over pay and conditions. On average, prison officers earn between £16,000 and £25,000 a year.

The anger of Walton staff has been fuelled by a local dispute over proposed new working practices at the jail, which unions say will lead to the loss of 30 jobs, an increase in unsocial working hours and more management-level staff.

Mr Baines added: "Staff are incensed by the way the governor is re-grading or abolishing their jobs without any consultation."

Since the 1919 Liverpool police strike, the POA has been legally obliged to give twelve months' notice that strike action would be its members' intention. But the union is exploring legal loopholes that might allow it to escape from the contract. The earliest date for action could be as soon as August 15.

The dispute does not affect Alt-course prison in Fazakerley, which is run by a private firm.

Prison numbers are at record levels, and the government is promising ever tougher sentences, yet they are awarding the prison officers with effective pay cuts. Prisons are there to protect the rich, since most prisoners are inside for crimes against property. And then of course there are political prisoners.

Free class war prisoners and free-up prison officers!