Ambulances were called out 200 times in six months to drug-related incidents at a prison which is failing to tackle the "serious problem", according to a report.

Improvements at HMP Wealstun, near Wetherby, are being undermined by "significant weaknesses", including the ready availability of drugs, inspectors found.

Psychoactive substances (PS) remained a serious problem and 200 of the 211 ambulance call-outs to the prison in the six months before the inspection were PS-related, according to the findings of an inspection carried out in October.

The category C training and resettlement prison in West Yorkshire holds 820 men, a third of which are under the age of 30.

Peter Clarke, the chief inspector of prisons, rated the prison's performance as good but said: "The ready availability of illicit drugs undermined much of what the prison was trying to achieve."

He said 69% of prisoners told inspectors it was easy to obtain drugs, and nearly a quarter of all prisoners said they had acquired a drug habit since entering the jail.

Mr Clarke branded this a "remarkable figure given the short time that many prisoners stayed there".

Wealstun was one of the jails in the 10 Prison Project launched in August 2018 by the then prisons minister Rory Stewart and was eventually given a body scanner and other technology to tackle drugs.

Mr Clarke said: "We were told that although the project had been set up in August 2018, support at a local level had not materialised until March 2019, and it could well be that the longer-term benefits of the project have yet to be felt.

"Until such time as there is a comprehensive action plan in place, that not only requires an effective response to intelligence but is also proactive in seeking out incoming supply routes, the harms caused by the ready availability of drugs will not be reduced."

Levels of self-harm had increased six-fold since the last inspection, the report also warned.

Mr Clarke added: "I have deliberately focused on a number of key weaknesses, because they inevitably undermined much of the very good work that was being carried out at Wealstun.

"I have little doubt that if the key areas of illicit drug supply and failure to assess risks were to be addressed, Wealstun could recover from the decline in grades since the last inspection, and indeed move on to better serve the needs of its prisoners."

He praised improvements including in areas like living conditions and healthcare.

Phil Copple, director general for prisons at the Prison and Probation Service, said: "The Governor and her team are working hard to address the issue of drugs at HMP Wealstun.

"The new X-ray scanner is bolstering security, and the prison is working closely with the police to catch those responsible."