PRISON officers are warning of a summer of riots in the North-East's jails if widespread overcrowding continues.

The alert came after three prison officers and an inmate were hospitalised after a disturbance involving 170 prisoners at Stockton's Holme House prison, last Thursday.

The Prison Officers' Association say the riot - the most serious at the flagship prison since it was opened in 1992 - was caused by overcrowding and Prison Service cuts in officer riot training.

An increasing number of flare-ups in Britain's prisons also prompted a warning by the deputy head of the Prison Service that riots are likely if overcrowding isn't tackled immediately.

In his report, published yesterday, Phil Wheatley, the deputy governor general, said: "There is a real risk that such incidents could escalate to involve large numbers of prisoners, leading to a major riot."

Reported in yesterday's Times newspaper, Mr Wheatley's report continues: "Overcrowding has increased instability in the estate and has contributed to a small, but significant number of incidents of mass disorder in our medium security estates, and some disorder in young offenders' institutions."

In last week's Holme House riot, one officer was slashed with broken glass and needed 15 stitches, while another was left with a broken collar bone. The injured officers are all out of hospital and recuperating at home, but are said to be "severely shook-up" by the incident.

The drama unfolded when eight staff were confronted by a mob of 170 inmates angry at being denied access to the gym because of overcrowding.

Two prisoners led the attack on the wardens, using smashed up jam and coffee jars - which were still being used despite safety warnings from union officials.

Wardens say they could have handled the riot better if vital "control and restraint" training hadn't been denied them recently. The room used to train officers in self-defence was being used for computer training instead.

Colin Moses, North-East official for the Prison Officers' Association, said: "We are the forgotten people of the front line and have been abandoned without proper training.

"Holme House is a flagship prison - the most modern in the public sector - but if this can happen here, it can happen all over the North-East. Staff are anxious about the next incident."

A Prison Service spokeswoman said that the jail, which was built for 950 inmates but now houses 992, is now calm. She said: "There have been delays in training, but they have now been resolved and that room is no longer used for computer training."