Justice Secretary Jack Straw has defended the use of so-called “vending machines”, including one in Shrewsbury’s Dana Prison, to dispense the heroin substitute methadone to prisoners.

Mr Straw said yesterday the machines would issue a controlled dose only to prisoners who had been prescribed the treatment, cutting down on the chance of deception. The Dana is among a number of prisons to have machines installed.

They automatically dispense methadone.

The machines, which allow prisoners to access the drug directly by scanning their fingerprint or iris, are already operating in 57 prisons.

A £4 million scheme will eventually see the machines installed in half the 140 prisons in England and Wales.

Details of the programme were released last week by the Tories and Opposition MPs today challenged ministers on the scheme in the Commons.

Tory Peter Bone, for Wellingborough, asked: “Could you explain why a dispenser is better value and better for the prisoner than going to see the medical officer?”

Mr Straw told him: “This is a most extraordinary confection of a story developed by some members opposite.

“Prisoners can only get methadone, whether it is dispensed through a machine or manually, having been to the medical officer because it is a dispensing machine.

“What happens is there is an iris scan, the machine recognises the prisoners – if it does – then the prisoner is dispensed with his dose, or her dose, of methadone and they have to drink it in sight of the prison officer and medical orderly.

“So there is no chance of deception of the kind I’m afraid takes place all too frequently otherwise in prison, especially with drugs.”

Justice Minister Maria Eagle said: “To refer to that as a vending machine is an absolute travesty of the truth.

“Vending suggests selling, that’s what the word means, there’s no question that the Prison Service deals in that kind of behaviour.”

By Russell Roberts