Legal high use in prisons has increased dramatically leading to violence and even deaths, according to official reports.
New figures demonstrate a seven-fold increase in the number of prisoners seeking help after using the drugs, also known as new psychoactive substances (NPS).
The news comes as the Government is seeking to introduce a blanket ban on NPS.
Legal highs played a part in at least 19 prison deaths between 2012 and 2014, according to a report by the Prisons and Probation Ombudsman.
And figures from the Rehabilitation for Addicted Prisoners Trust (RAPt) show a massive increase in the number of inmates seeking help for NPS use.
Between April and September last year, 87 prisoners sought help with problems related to legal highs. This year 622 prisoners sought help during the same period.
The figures from the RAPt represent 26 prisons across the country. But the problem is reckoned to be much worse because there are over 130 prisons in the UK.
Chief Executive of RAPt Mike Trace told the BBC: “Our frontline teams have seen an alarming surge in the use of new psychoactive substances in just the last year.
“Staff are reporting distressing levels of violence, both from the effects of these drugs but also the lucrative market exploited by gangs.”
The Chief Inspector of prisons in England and Wales, Nick Hardwick, said: “People have died” and have been made “very ill” because of the lucrative trade of legal highs which goes on in prisons.
He added that growing violence associated with legal highs is a “rapidly escalating problem” which is “getting worse by the day”.
The Government has launched a Bill to crack down on legal highs by introducing a blanket ban.
Currently in the UK, individual legal highs are banned on a case-by-case basis but manufacturers are able to get around the law by tweaking the chemical composition of the drugs.
The Psychoactive Substances Bill will make NPS illegal, based on the “psychoactive” effect they have.