New Hall prison had seven heads of security in only three years
Security measures at a prison in West Yorkshire have been criticised after inspectors found that illegal drugs were being posted to inmates.
Lax checks allowed inmates to receive drugs at Wakefield's New Hall prison, the HM Inspectorate of Prisons said.
Inspectors said some mail room staff lacked an awareness of drug security and only nine prisoners were searched for drugs in one three-month period.
The Prison Service said its search procedures were "robust and effective".
The Prison and Young Offender's Institution holds nearly 400 women and girls.
Increase in use
The report said: "The main route into the prison was through the mail.
"Staff believed that mail was a particularly vulnerable area and there had been eight finds in mail in one month."
There had been seven heads of security at New Hall in only three years, undermining efforts to tackle the drug problem, inspectors said.
A survey of prisoners found only 10% said it was difficult to buy drugs, while 41% said it was easy.
The report said the programme to tackle drug abuse was "disjointed and lacked leadership".
A Prison Service spokesman said: "The number of drug seizures at HMP New Hall make clear that its search procedures are robust, effective and are making a difference in disrupting the supply of drugs into the prison.
"We take the issue of drugs in prison very seriously, and will seek the conviction of any individual attempting to smuggle drugs, or any other banned item, into prison.
"Prisoners who break the rules will be subject to disciplinary procedures."