Offenders are going back to crime to pay off drug debts racked up behind bars, a watchdog report suggests.
Prisoners told researchers that increased tolerance to the substance known as Spice led to them smoking between five and eight grams per day.
The assessment from HM Inspectorate of Probation said: "Their level of dependency led to debts building, with prison prices being up to one hundred pounds per gram.
"Those in debt were often involved in violent incidents where threats were made to family members, with some stating that they offended to repay the debts they had built up in prison."
Spice and other new psychoactive substances (NPS), formerly known as legal highs, have been identified as a major factor behind surging levels of violence that have hit much of the prisons estate in England and Wales.
Chief Inspector of Probation Dame Glenys Stacey said work to tackle the prevalence, impact and treatment of NPS was lagging behind their use by offenders in the community.
She said: "We found that probation staff and even some substance misuse service staff had a low level of awareness of NPS.
"Probation staff did not have structured, in-depth training about NPS and how to deal with dependency, and lacked the confidence and knowledge to quantify the problem and to address it."
The report raised concerns that risks to children were not fully assessed.
It said: "We saw case records where responsible officers were aware that service users who reported using NPS daily were on their way to see their children. Such safeguarding concerns had not been sufficiently analysed."
The inspectorate makes clear that NPS use is still relatively limited compared to abuse of alcohol and drugs such as cocaine and heroin.
However, it notes that offenders under probation obtain Spice and other NPS because they are cheap and difficult to detect in tests.
One probation officer said: "People are crazy when they are under the influence, one confused me for a fire hose when he was under the influence."
A Ministry of Justice spokesman said: "The easy availability of psychoactive substances in the community is an issue that compounds the difficulty of reducing supply in prisons.
"That is why we are working with agencies across the criminal justice system to address this problem.
"Training for staff on working with other local organisations - such as healthcare and thepolice - on how best to address the use of psychoactive substances is also being boosted to ensure we have a co-ordinated strategy on the ground to tackle these issues."