Prison suicides will only decrease if more people are taken out of the jail system, says a penal reform charity.

The Howard League says many people with a history of social problems, such as mental illness, are unnecessarily imprisoned.

It believes jail increases their problems and may push some over the edge.

The number of prisoners committing suicide in Britain's prisons has been rising in recent years after a decline in the mid-1990s.

Between 1997 and 1998, they rose by 22%.

The report, Desperate Measures: Prison Suicides and their Prevention, says overcrowding in prisons puts a strain on resources, meaning those at risk of suicide are not identified and properly care for.

It said 65% of the 515 people who committed suicide in prison between 1990 and 1998 died in a local prison where many are locked in their cells for 23 hours a day due to overcrowding.

The majority were on remand and had not been convicted of any crime.

A third had a history of mental health problems.

The report says prison should be used as a last resort.

Sea-change

Frances Crook, director of the Howard League, said boredom, isolation and lack of meaningful activity played a role in many of the deaths.

"We believe that a sea-change in prison culture and standards is needed to deal with this problem.

"Such a shift can only come about if the government acts to reduce numbers going to prison and improves conditions for those who have to be there.

"The Prison Service will continue to fail to keep people alive as long as the courts percieve imprisonment as an option for non-violent and mentally disordered offenders."

The report comes the day after the Office for National Statistics released figures showing a strong link between mental illness and imprisonment.

It says a fifth of male prisoners and two fifths of women prisoners have attempted suicide at some point in their lives.

The Howard League report recommends better training of prison staff regarding suicide awareness, that those with serious mental health problems should not be imprisoned and that screening for suicide risk on reception be improved.

It says more effort should be devoted to reducing the stress prisoners experience when they arrive in jail and it says staff should attempt to be more supportive.

The report also calls for a ban of strip cells for suicidal prisoners and for more accurate record-keeping of suicide and self-harm attempts.