Synthetic cannabis is having an unprecedented and destabilising impact on prisons, according to the chief inspector of prisons.
An officers' union has warned that prisons are "awash" with the drug, also known as "spice" and "black mamba", one of a suite of so-called "legal highs" suspected of contributing to deaths, serious illness and self harm in both male and female institutions.
Meanwhile some prison staff reported falling ill after entering contaminated areas and others have been attacked by high inmates, the Prison Officers' Association (POA) said.
The man-made narcotic is hard to detect and there are reports of packages being dropped into prisons by drones and thrown in over walls, The Press Association reported.
Inmates hooked on the drugs are racking up large debts with pushers and there are increasing levels of bullying and violence as a result, the chief inspector said.
Peter Clarke, who was appointed in February, told the Guardian that the situation appeared to be "getting worse, not better".
"Prison staff have told me that the effect on individuals and prisons as a whole is unlike anything they have seen before," he said.
A 2015 report by the Prisons and Probation Ombudsman (PPO) found 19 fatalities over a two-year period where the inmate was known or strongly suspected to have taken new psychoactive substances (NPS), of which synthetic cannabis is used the most widely.
Rather than being derived from the cannabis plant-like resin or the more potent "skunk weed", the synthetic version is a chemical compound cooked up in clandestine laboratories that brings on similar effects of the naturally occurring, psychoactive tetrahydrocannabinol (THC).
However, the synthetic forms of the drug are much more powerful.
Investigations by the PPO uncovered examples of "erratic, violent and out of character" behaviour by prisoners suspected to have used NPS.
The drugs were suspected of being a "relevant factor" in the deaths, with some cases involving prisoners who died after they fell ill or took their own lives after taking the synthetic drugs. Many had taken the drugs in cocktail with other illegal substances, or had been taking prescribed medication.
They included one male who died after being given "spiked" cigarettes and a female said to have died after taking NSP and cocaine before making a deep cut in her arm.
Mr Clarke told the newspaper strategies are needed at a local and national scale to tackle their supply and treat affected inmates.
He said: "NPS is having a devastating impact in some of our prisons, more severe than we have seen with other drugs.
"Their presence in prisons has given rise to debt, bullying and violence. They are destabilising some prisons, making it difficult for normal prison life to continue."
The PPO said, because the drugs are generally odourless and have hundreds of variations in chemical make-up, their use proved difficult to detect and to manage.
However, the POA has accused the prison service of failing in its duty of care for prisoners and prison staff and said the Government was not taking the problem seriously enough.
General secretary Steve Gillan told The Guardian: "Our prisons are awash with synthetic cannabis and prisoners are so out of their heads they don't know what they are doing sometimes. They are a danger to themselves, they're attacking staff, and they are attacking other prisoners."
The prison service told the newspaper it was using sniffer dogs, cell searches and mandatory drugs tests and new laws mean those caught smuggling NPS into prisons face up to two years in jail.
