The drug problem at Wandsworth prison, Britain’s biggest jail, is spiralling “out of control”, sources have claimed, with drug packages thrown over prison walls “almost daily”.

Shocking revelations – including cell doors that do not close properly and drugs being passed mouth to mouth between inmates – come as the prison’s annual Independent Monitoring Board Report (IMBR) again said Wandsworth’s prison’s drug trade was worth £1m annually.

The IMBR said 70 per cent of inmates were sentenced for drugs and drug-related offences with 300 – or 18 per cent of inmates as of June 2009 – hooked on the heroin substitute methadone.

The Prison Service said it took the drug problem seriously and had introduced new security measures.

One source said: “Some drugs come in through the door by guards and others but most gets dropped over the walls, it is out of control.

"An inmate phones someone outside and says, ‘We will be in the yard in five minutes’. Then, five minutes later, the package comes over.

"The cons [convicts] stand in a group and distribute it in two minutes flat. They divide it up, hide it up their bum, in their mouth, anything. When they disperse you don’t know who has got what.

It happens almost daily.”

A source said cell doors in the drug rehabilitation wing did not close properly and eye-recognition software, which is used to safely distribute methadone, did not work.

They said: “You can’t close the viewing flap on the cell doors, so inmates can pass stuff to them. Authorities are aware but it means you can’t keep a prisoner in isolation.”

Another source said: “One of the first things [inmates] are given is their methadone. New inmates hold on to this in their mouths, spit it out and then sell it to other inmates so they get a double hit.”

Another added: “After an inmate is hooked [on drugs] they will go to any lengths to feed their habit. What these guys do does beggar belief. They will tell their girlfriends, mums, anyone that if they don’t get money they will be beaten-up.

“They put lots of pressure on them and say the next time they will see them will be in the morgue or hear about them at Westminster Coroner’s Court.”

The IMBR noted the iris recognition software was “currently out of use” and a Body Orifice Search Scanner (Boss) chair, used to detect phones and drugs coming into the prison, was broken.

A Prison Service spokeswoman said: “We take the problem of illicit drugs in prisons very seriously and work to do everything possible to disrupt their supply and demand... including the use of search dogs and close working with local police.”

She added the Boss chair had “maintenance problems” but staff were using hand-held metal detectors to catch mobile phone smugglers.

Figures obtained by this paper showed the number of mobiles – which the IMBR said were used to fuel the drug trade – confiscated from prisoners had risen.

Two weeks ago prison officers said targets to reduce restraining technique meant staff were “becoming scared to do their jobs”.

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