Rapidly rising numbers in jails are having a "debilitating and chilling effect" on prisoners and suicides are becoming more common, the prisons' inspector has warned.

In a frank report on the crisis in the prison system, the chief inspector of prisons Anne Owers warned rehabilitation of prisoners was being neglected with inmates often locked in cells for 23 hours a day.

This has undermined work to prevent inmates reoffending - meaning the public was at increased risk, she said.

The debilitating and chilling effect of prison overcrowding threatens all four of the Inspectorate's tests Anne Owers Chief prison inspector

Ms Owers' report comes a day after the Home Office revealed that prison numbers are likely to rocket.

The current record population of 73,000 could rise to 110,000 across England and Wales by June 2009 in the service's worst case scenario.

"There can be no doubt that most prisons are less safe than they were a year ago and many are also less decent places," Ms Owers said.

"They will be less able to protect the public by reducing reoffending.

"The debilitating and chilling effect of prison overcrowding threatens all four of the Inspectorate's tests of a healthy prison - safety, respect, purposeful activity and resettlement."

Radical campaign

Her concern about rising suicide rates comes as the prison service plans a "shocking" poster campaign to warn inmates about the realities of suicide attempts.

It is hoped the radical campaign will help save the lives of inmates who accidentally kill themselves making "cries for help" in cramped prisons.

The prison population rose 7% in the first nine months of the year, with the authorities forced to house prisoners in police cells as an emergency measure.

There has been concern that poor conditions are fuelling violent disorder as well as suicide.

Proper resources

In one recent week, eight people killed themselves in prison.

And there were as many suicides by the end of September as there were in the whole of 2001.

Overcrowding was also blamed for an eight-hour riot at Lincoln prison in October which caused �1m of damage.

Ms Owers concluded: "There are choices to be made. Prisons that are properly resourced and supported, and that are used only where necessary, can deliver positive work that provides long-term public protection by reducing reoffending.

"Or they can be 'Operation Container' - warehousing prisoners and firefighting to limit the damage to them or the prison system."