Thousands of British prison officers have stopped working in protest over a system "in meltdown", union leaders said Tuesday, prompting the government to take legal action to force them back on duty.

The 24-hour protest caused disruption in British courts -- halting the high-profile murder trial of a man accused of killing MP Jo Cox -- after talks between union bosses and the government broke down.

Britain's largest prisons union, the Prison Officers Association (POA), directed its members to take part in the action over what it described as the "volatile and dangerous state of prisons".

Justice minister Liz Truss said the government was seeking legal redress over the matter, since prison officers in Britain are technically banned from going on strike.

"The union's position is unnecessary and unlawful and it will make the situation in our prisons more dangerous," Truss told MPs in the House of Commons.

The government has appealed to the High Court for an injunction to block the action, the Ministry of Justice (MoJ) confirmed.

Joe Simpson, assistant general secretary of the POA, said 10,000 members around the country were participating in the stoppage, but insisted it was "not a strike".

There are around 85,000 prisoners in Britain.

Incidents of violence, self harm and deaths in custody have been "steadily rising", reaching "totally unacceptable" levels, he told AFP.

The protest comes after a series of recent incidents at British prisons including a riot involving up to 200 inmates, the fatal stabbing of an inmate, and the escape of two other prisoners.

The POA blamed the problems on "chronic staff shortages and impoverished regimes".

"The continued surge in violence and unprecedented levels of suicide and acts of self harm, coupled with the recent murder and escapes demonstrate that the service is in meltdown," the union said in a statement.

An MoJ spokesman said there was "no justification" for the action as the government had addressed union concerns, including with an additional 2,500 frontline officers.

The trial of Thomas Mair, accused of killing mother-of-two Cox a week before the EU referendum in June, was adjourned until Wednesday morning at London's Old Bailey central criminal court.