An eight-hour riot at Lincoln Prison was caused by overcrowding, a prison governors' leader has claimed.

Prison Governors' Association (PGA) President Mike Newell said there could be riots in other jails if the prison population is not reduced.

He said the PGA had repeatedly asked Home Secretary David Blunkett to do something about overcrowding, but was unhappy with the response.

Prison Service Director General Martin Narey has already stated he did not think overcrowding was the cause of the disturbance.

Martin Narey has defended the jail

An investigation has started into why trouble broke out at 2010 BST on Wednesday night.

So much damage has been done that hundreds of prisoners have been moved to other institutions.

The prison population in England and Wales stood at 72,517 last week - up 4,500 in the last 12 months alone.

Lincoln, which was built in 1872 and has more than 500 inmates, was operating at full capacity.

Mr Newell, governor of Durham Prison, told the BBC: "It is quite clear that there has been an increasing level of tension in the service, caused by overcrowding. There have been more and more incidents.

"We are in a real state of tension. When we are in that state, there is an increased risk in all our prisons, particularly our local prisons, for serious incidents.

"Unless we do something about the population, we shouldn't be surprised if we have more difficulties."

Decent treatment

David Wilson, professor of criminal justice at the University Central England in Birmingham, said: "The dirty little secret of our prisons is that they only run with the consent of the prisoners.

"They withdraw this consent when they feel the prison is no longer being run fairly."

Mr Narey defended the prisons as being more than just secure units.

He said: "We are trying to treat prisoners decently and educate them and make them more employable."