Winchester Prison has one of the worst drug abuse problems of any jail in the country, according to recently-published research.

The report, by the Prison Reform Trust, shows illegal drugs are rife at the Romsey Road jail, with the rate of positive random drug tests 28.5%, against a government target of 10%. The category B male local prison has the third-highest rate of positive tests in England and Wales.

The study, A Measure of Success, uses Home Office data for 2003-04 to give a snapshot of conditions in jails across the country. It highlights the problem of severe overcrowding at Winchester as the prison population soars nationwide.

Six out of ten prisoners are sharing cells designed for one and having to defecate in front of each other. This compares to an average rate of doubling up in a single cell of 21%. At present, around 641 prisoners are crammed into the ageing Victorian jail.

The Prison Reform Trust notes that it was because of population pressure that Westhill women's section of Winchester Prison was relocated to make room for men, "uprooting the first therapeutic community for women in Europe".The female inmates were moved out earlier this year.

Winchester also has one of the highest rates of self-inflicted deaths in custody. Four prisoners committed suicide in 2003 - although no inmates have taken their own lives in the last 11 months.

A spokesman for the trust said: "We tend to find that local prisons have the worst conditions, the highest turnover and the most overcrowding because they receive prisoners immediately from courts and have to accommodate them."

Alec Rowley, assistant governor of Winchester Prison, said there had been a clampdown on drugs in recent months, with use of sniffer dogs and CCTV, more rigorous searching of visitors and intelligence-led drug testing of inmates.

He said only 13.9% of prisoners tested positive in computer-generated random drug tests last June. "We take the whole issue very seriously and since the figures were published, have made great strides in reducing drugs in Winchester Prison. We don't want drugs in the prison, as it creates an unsafe environment for both staff and prisoners."

He said overcrowding was a national problem and local prisons bore the brunt of the increasing numbers going into custody. "Certainly, we do have many prisoners who share cells."

But Mr Rowley stressed there had been no suicides in the last 11 months. "Considering the mix of people held in these conditions, that is very good. We have a full-time suicide prevention co-ordinator who holds a management position here."

* Escapes from Winchester Prison should be even more difficult in future. HM Prison Service has submitted a planning application to upgrade the external security fence. Proposals include reinforcing the existing wall with metal sheeting and building an additional, taller wall within its perimeter.

Mr Rowley, said: "It is an upgrade in line with new requirements for security."

The last prisoner to escape from Winchester Prison was convicted killer, William Todd, in December, 2001. He used a home-made grappling hook and rope to scale the 30-foot wall. He was eventually recaptured after an extensive manhunt which ended in Pangbourne.