Prison bosses desperate to keep their jails under control amid record levels of violence have resorted to "draconian" punishments that are only making the problem worse, a campaign group has said.
The use of disciplinary hearings, known as adjudications, to punish inmates who break the rules has piled pressure on already overcrowded prisons, the Howard League for Penal Reform said.
The charity branded the system "a monster" and said it was unfairly targeting children and vulnerable adults, including people who are mentally ill or self-harming.
Ministry of Justice figures show inmates were handed an extra 215,000 days – or 590 years – of additional imprisonment last year, an increase of 30% from 2014 and 80% since 2010.
These mainly resulted from disobedience, disrespect or property offences, which all increase as conditions in prisons deteriorate, the charity said.
The development comes as prisons across the country have been under unprecedented pressure due to overcrowding, a lack of staff, and record levels of violence.
The Howard League said while the adjudications were originally intended as a way to manage serious breaches in conduct, they had now become routinely used by prison governors as a "behaviour management technique" in out-of-control jails.
Frances Crook, chief executive of the Howard League, said: "Instead of solving the problems, these punishments feed a vicious cycle, piling more pressure on the prison population and worsening overcrowding, which in turn creates conditions for drug abuse and violence.
"At the same time, rules to incentivise prisoners' behaviour have been made more punitive, which is also contributing to the poisonous atmosphere behind bars."
Strikes over concerns over safety
The charity cited one case where a prisoner being bullied by other inmates had been dragged to a disciplinary hearing because he refused to return to his wing, fearing he would be attacked.
In another case, an inmate said that he was punished after trying to break up a fight between other prisoners.
The charity's report comes just days after up to 10,000 prison officers stopped working during a strike over concerns over safety behind bars.
A number of high-profile incidents in prisons across the country in the past month have piled pressure on Justice Secretary Liz Truss to do more to ease the pressure behind bars.
This includes the fatal stabbing of a young inmate at HMP Pentonville; the escape of two prisoners from the same jail; the rioting of about 230 prisoners at HMP Bedford; an incident which saw a prison officer's throat slashed at HMP Isle of Wight; and a mini-riot at HMP Exeter during which a prison officer was reportedly held hostage.
The Howard League said many of the problems facing the prison service could only be solved by reducing the record 85,600 people currently behind bars in England and Wales.
The government announced earlier this month a range of prison reforms intended to reduce violence and improve rehabilitation.
A prison service spokesman said:"We want our prisons to be places of safety and reform, and so it is right that offenders who break prison rules are properly punished. Where this amounts to a criminal offence, prisoners should expect to be investigated by the police and face more serious sanctions.
"We have announced a major shake-up of the prison system, with 2,500 extra prison officers and new security measures to tackle violence, drones, phones and drugs.
"In our White Paper, we set out plans to review the current discipline system to deal with low-level disorder in our prisons, and we plan to give governors more powers to run their prison the way they think best."