Up to 80 per cent of prisoners test positive for hard drug use when they begin their sentences, the Director General of the Prison Service says.
Phil Wheatley warned of the extent of addiction to opiates, including heroin, and cocaine among new inmates and remand prisoners in an interview today with The Independent.
He said 55 per cent of those entering prison were classified as "problematic" users of illegal drugs, including cannabis, with a further 25 per cent reporting some drug misuse.
But the trend is even more acute in some urban jails, where 80 per cent of new arrivals are found to have "class A" drugs in their system, indicating they had been taken within the previous 48 hours.
"The number of prisoners who come in who have got substantial drug habits has increased over the years," Mr Wheatley said. "Making sure we can detox people successfully is important." The prison service put 50,700 inmates on detoxification programmes in 2002-03.
Juliet Lyon, the director of the Prison Reform Trust, said the numbers indicated "both that the current drugs policies are failing and that prisons are being asked to take up the slack for the lack of treatment in the community".
Detoxification programmes are improving, Mr Wheatley said, with the numbers of positive drug tests among serving prisoners halving in the past six years. However, 11.7 per cent of prisoners were using some illegal substance and 3.6 per cent had taken opiates.
It was impossible to stop any drugs reaching inmates, he said, adding: "It's not possible to hermetically seal a prison."