Spice: the drug 'more devilish than weed' sweeping British prisons – by Symeon Brown, Tom Silverstone, Mary Carson, Maggie O'Kane and Irene Baqué guardian.co.uk

Synthetic cannabis known as "spice" or "black mamba" is a growing problem in UK prisons with serious physical and mental health consequences, the chief inspector of prisons, Nick Hardwick has said.

Its popularity with inmates has surged because the psychoactive designer drug can be passed off as a tobacco roll-up, has no distinctive smell and it evades current drug testing capabilities in prisons.

In a Guardian Films investigation, we spoke to several prisoners, former prisoners and officials and analysed Her Majesty of Prisons Inspectorate (HMIP) reports that revealed it had become a problem in at least 28 prisons in England.

Several former prisoners said the drug was rife inside, having been thrown over the walls or otherwise smuggled in, and one said its lack of smell meant it could be smoked in front of the guards. Another, a remand prisoner currently at HMP Forest Bank near Manchester, said in a telephone interview that some of those using it were "going down like flies". He said it had led to multiple calls to the emergency services.

"I've never seen anything like it in prison. Guys are taking it and having psychotic episodes all over the place. Ambulances are coming in and out of the place more frequently than the escort vans," he said. It is not clear how many of these incidents involved other drugs in combination.

The recent annual Global Drug Survey (GDS), which surveys thousands of drug users on their experiences, indicated that users of synthetic cannabis were seven times more likely to need hospital treatment than users of the natural form of the drug. Several deaths in the US have been blamed on spice, which is made from dried plants sprayed with engineered chemicals.

"What we can say for definitive is that spice is a significant problem in a number of prisons and it is rising," Hardwick told the Guardian.

"As opiate-based drugs become less popular, spice has become a more favoured option. We've seen examples where its affected people's heart and so have had to have emergency treatment. It has affected people's mental health and what it it seems to do is exacerbate people's existing conditions".

There was currently no effective test for the drug, he said.

The HMIP reports describe prisoners who have taken the drug experiencing seizures, psychosis, loss of motor control and an irregular heartbeat. At HM Prison Ford in West Sussex, the prison's drugs and alcohol recovery team said 85% of its prisoners were using or supplying spice.

A government ban on spice-like drugs in place since 2009 does not cover many newer and often more potent versions as the chemicals used to synthesise them are different. . Spice-like drugs can still be bought on the high street and online on the basis that they are not for human consumption.

At HMP Wealstun in West Yorkshire, a notice issued to practitioners and visitors to the prison and made available to the Guardian reveals that in a two-week period in March, 13 prisoners required medical attention after using synthetic cannabis, and five cases were so severe that they were rushed to hospital.

Glyn White, 35, who has served time in more than 15 prisons including Norwich, Leicester, Weyland and Ranby, said he first noticed synthetic cannabis in 2006. He first smoked it in 2012, and said he witnessed grown men experiencing breakdowns. "I saw people pass out. I saw people cut themselves. I took it and had to go to my cell for a couple hours because that buzz is intense when you ain't had no weed," he said.

"I went to Weyland. It just exploded there. It was selling for £100 a gram. That is better than selling the buds [natural cannabis]. It don't smell and is easier to conceal. When I got out of prison I started smoking a bit of it, but I reckon its worse than weed."

Dr John Ramsey, a toxicologist based at St Georges University London, told the Guardian that testing for drugs such as spice was difficult because manufacturers change their composition changes so often. "The number of chemicals you can think of that would mimic cannabis is a very, very large number. Whatever you do, you can probably tinker with the molecule and find a way around it because they are a very diverse group of compounds."

The list of drugs prisoners are tested for has not been updated for five years and does not include synthetic agents, but a Ministry of Justice spokesman said it had commissioned scientists to devise a test for new psychoactive substances.

The government has also introduced an amendment to the criminal justice and courts bill to expand prisons' power to test for non-controlled drugs.

The spokesperson told the Guardian: "Prison staff take the use of any illicit substances in prison extremely seriously and use a range of robust measures to find them, including interrogation, intelligence, searches, specially trained dogs and random drug tests. Anyone caught with them will be dealt with severely and may be referred to the police for prosecution.

"The misuse of new psychoactive substances is an issue affecting many parts of society, including prisons."

The psychoactive chemicals tend to be imported from pharmaceutical companies abroad, most notably in China, and then blended in the UK.

The terms spice initially referred one brand of synthetic cannabis, but now all forms of the drug. Other names also include K2 and clockwork orange.

Additional reporting by Eric Allison