A prison in Wiltshire has scored badly in new Ministry of Justice figures revealing the extent of drug abuse among inmates.
The jail, which houses some 350 inmates, recorded the second-highest level in the country of positive tests for heroin and other opiates.
More than one in six prisoners were found to have used Class A drugs.
The Justice Minister said a review is under way into disrupting drug supplies and is due to be complete by May.
The figures showed the highest level of opiate abuse - 16.7% of inmates - was uncovered in random tests at Featherstone prison in Wolverhampton.
Out of 139 prisons in England and Wales, 38 were clear of positive opiate tests.