Prison drug use

25% Cardiff, south Wales 25% - Everthorpe, east Yorkshire 26% - Leicester 30% - Blakenhurst, Worcestershire 34% - Featherstone, Wolverhampton

The nationwide inquiry found the Prison Service in England and Wales was failing in eight of its 18 performance indicators.

Only prisoners in Wolverhampton, Worcestershire and Leicester were heavier drug users than at the Cardiff jail.

The Prison Service has defended the findings. A spokesman said they merely reflected the extent of drug use outside of Cardiff Prison.

Visitors bringing drugs in to the building were cited as a constant problem and extra surveillance equipment is being set up in an effort to detect the smuggling.

A worrying number of prisons are overcrowded, unsafe and provide inadequate purposeful activity for prisoners

Joe Levenson, report author

The spokesman said Cardiff was a local prison with many remand prisoners in its 500-strong population and frequent visitors.

Usk Prison, however, was at the opposite end of the league table. Findings showed just 2% of positive drug tests - a sign of an older population.

A rise in the number of inmates in jails across the UK has been sited as a contributory factor to the drugs problem.

Author of the report Joe Levenson said: "The Prisons League Table shows that despite some progress the Prison Service is struggling to cope with a record prison population.

'Failing prisons'

"A worrying number of prisons are overcrowded, unsafe and provide inadequate purposeful activity for prisoners.

"Until these failing prisons are drastically improved, prisoners will continue to be held in damaging conditions with little to be done to prepare them for release."

The study revealed that Featherstone Prison in Wolverhampton had the highest number of drug users for the second year running.

But other findings were more alarming. 93% of inmates at Castington Young Offenders' Institution (YOI) in Morpeth, Northumberland, were assaulted last year - more than 10 times the national target of 9%.