The walkout took the government by surprise

All 129 non-private prisons suffered disruption after the surprise walkout by about 20,000 staff at 0700 BST.

A High Court injunction was granted against the Prison Officers' Association (POA) but many members initially refused to go back to work.

The government had called the strike illegal and unjustified.

It denied it had failed to address concerns about pay and falling morale among prison staff.

Court order

The strike action came after the union pulled out of a no-strike agreement with government.

The POA said the government had failed to deliver on "promise after promise" and it decided to call the strike without prior warning to avoid attracting a court order.

POA general secretary Brian Caton said: "If they gave us back our rights and put us under the restrictions that every other trade union is under, then they would have had that notice.

"After a day of what we describe as somewhat traumatic times in the history of the union, we will lead our membership back to work and we will do that in an orderly fashion and that is regardless of any court injunction."

Justice Secretary Jack Straw said: "I am glad that the POA has issued this instruction to return to work."

A spokeswoman said Mr Straw had arranged to meet the union's leadership on Friday, before he knew about the strikes.

'Widespread' action

The announcement to end the strike came after officers in Bristol, Canterbury and Long Lartin had returned to work in the afternoon, but other POA members were indicating they would stay out for 24 hours.

During the day, prisoners were kept locked in their cells, senior managers took charge of duties such as distributing meals and visitors were turned away.

PRISON OFFICER SALARIES Auxiliary staff: £13,318 Storeman: £14,942 Night patrol: £14,084 Entry officer min: £17,744 Prison officer: £27,530 Senior officer: £29.371 Principal officer: £31,913 Recommended top pay in posts as of April 2007. Source: Office for Manpower Economics

An independent pay review body for prisons has recommended that salaries rise to between £12,000 for auxiliary staff to almost £32,000 for principal officers - a 2.5% increase.

But the POA, which has 28,000 members, said its value is reduced to below inflation by being introduced in two stages.

Among the prisons affected were: