Correspondence is being exploited to convey illicit substances and items into establishments, according to an official security briefing seen by the Press Association.
Instances have been reported in all prison regions in England and Wales, and in both the male and female estate.
Finds have included “large amounts” of drugs, tobacco and sim cards, the document circulated by HM Prison & Probation Service says.
It also reveals that some jails have reported chemically laced paper containing household chemicals such as alloy wheel cleaner, insect poison, koi carp sedative and acetone.
Prisons Minister Rory Stewart said scanners which can detect invisible traces of drugs soaked into clothing and paper have been installed at 10 of the most challenging jails.
He said drugs in prison have been a “game-changer”, driving self-harm and extreme violence, adding: “As the methods used to smuggle drugs into prisons continue to evolve, our response to that threat becomes ever more agile and vigilant.”
Smuggling attempts involving mail have come under the spotlight after psychoactive substances such as Spice were identified as a major threat to prison stability.
The drugs, formerly known as “legal highs”, have had a “significant” impact on the safety and security of establishments, the briefing note says.
The official guidance, obtained by the Press Association following a Freedom of Information request, says intelligence continues to suggest that paper laced with psychoactive substances (PS) is being supplied via correspondence.
It states: “The potency of PS paper can vary significantly between batches and even within different sections of a single sheet.
“As our ability to detect herbal PS and interrupt conveyance has improved, prisoners have increasingly sought to convey PS-soaked paper as it is easier to conceal.
“Actual levels of laced paper entering the establishments are not known; however, intelligence reporting indicates that post appears to be the preferred method.”
The briefing, marked “Official”, was issued to governors, security departments and mail room staff in November.
It says: “Whilst it is recognised that mail is one method in which prisoners may receive illicit items, we should not introduce processes that indefinitely treat all such correspondence as suspicious.
“Where justified, we should open, read, and stop mail on a case-by-case basis.”
Staff members who suspect that mail contains illicit items are advised to wear personal protective equipment for health and safety reasons and evidence preservation, the five-page paper says.
Photocopying correspondence and providing prisoners with copies of the original letters may be considered if it is proportionate to the risk posed, the guidance says.
Any establishment that imposes this measure for all post should review the position at least every three months, while legal and confidential mail can only be photocopied if there is “specific intelligence or suspicion”.
The document recommends that prisons communicate with law firms to ensure genuine correspondence is correctly marked, following warnings about the use of bogus legal letters for smuggling attempts.
Where there is a local supplier of newspapers and magazines, jails should consider using more than one to “disrupt potential conveyance activity in this area”.
The document emphasises that “due care should be given not to significantly delay a prisoner’s access to mail, in the interest of ensuring minimal impact on family life”.
Peter Dawson, director of the Prison Reform Trust, said: “This guidance shows why tackling drugs in prison is more complicated than people sometimes like to think.”
He suggested a straightforward way to reduce the problem would be to give prisoners “controlled access” to electronic communications, adding: “You can’t spray Spice on to an email.”
Mr Leech said: “Drugs are a menace in our prisons leading to violence, bullying, self-harm and suicides, anything that reduces the importation into prisons of drugs is to be welcomed.
“But installing scanners in less than 10 per cent of prisons is woefully inadequate, the Prisons Minister needs to get real and install them across the prison estate.
“Prison governors can authorise the opening of mail between inmates and social contacts to check for illicit enclosures, and they also have the power to open legal correspondence, and read it, where there are grounds for believing that it contains illicit enclosures or doesn’t come from a bona fide legal source.”
The latest prison safety statistics will be published at 09.30 today – Thursday 31st January 2019.