Prison numbers are set to rise further

This was one of seven out of 15 performance targets that the service failed to meet in the last year.

A total of 105 people killed themselves in jail in the year to April, up from 74 the previous year.

The service also failed to cut the number of positive drugs tests among prisoners, which rose over the year.

The head of the Prison Service, Phil Wheatley, said the failure to reduce suicides had been his "biggest disappointment".

Other missed targets included the reduction in positive drug tests and cutting the staff sickness rate: each officer took about 14 days off work a year.

However, the figures suggest there has been an improvement in prison security.

Only five prisoners escaped last year - the lowest level ever recorded.

Overcrowding crisis

The report comes as a Home Office official warned the Prison Service may soon have to begin sending inmates to police cells because the jails are full.

Second permanent secretary Martin Narey told MPs the number of inmates in England and Wales was likely to reach 80,000 within three years.

But he told the all-party Home Affairs Select Committee the escalating prison population, which is causing an overcrowding crisis and has been blamed for rising suicides, was actually growing less fast than predicted.

Mr Narey, who is also the Commissioner for Correctional Services, overseeing both prisons and probation, said: "The prison population is significantly undercutting the most recent projections.

"We are just waiting for new projections to be worked on at the moment.

"There is every sign that the population will reach in the region of 80,000 by about 2005-2006."

Current predictions say numbers will be between 87,000 and 100,000 by 2006, and up to 110,000 by 2009.

The absolute maximum number which can be accommodated is currently 76,400, due to rise to 77,000 by the end of the year and to 81,000 by March 2006, he added.