Troublemakers behind bars at Lincoln Prison have had more than 1,000 days added to their sentences for unruly behaviour in the last 12 months.
A report from the Howard League for Penal Reform has revealed that inmates at HMP Lincoln were handed a further 1,063 days in prison in 2014.
Nationally, almost 160,000 days – or 438 years – of additional imprisonment were imposed on prisoners found to have broken prison rules last year.
The report has looked at how jails in England and Wales operate disciplinary hearings where allegations of rule-breaking are tried.
The hearings, which cost between £400,000 and £500,000 a year in total, mainly concern disobedience, disrespect or property offences.
A prisoner found guilty at an adjudication faces punishments ranging from loss of canteen to solitary confinement and extra days of imprisonment.
The report has shown that the number of adjudications where extra days could be imposed has increased by 47% since 2010.
The number of extra days imposed on children has almost doubled in two years – from 1,383 in 2012 to 2,683 in 2014 – even though the number of children in prison has almost halved.
A rise in the number of adjudications has come at a time when prisons across England and Wales are struggling to overcome problems caused by a growing prisoner population, chronic overcrowding and cuts of almost 40% to frontline staffing.
Lincoln Prison, one of the most overcrowded in the country, has had a 42% reduction in staff numbers since 2010.
Frances Crook, Chief Executive of the Howard League for Penal Reform, said: “The system of adjudications has become a monster, imposing fearsome punishments when people misbehave often as a result of the dreadful conditions they are subjected to.
“This bureaucratic, costly and time-consuming system of punishments then further feeds pressure on the prisons, creating a vicious cycle of troubled prisons and troubling prisoners.
“The principle of independent adjudication where liberty is at risk is an important one. But prisons have come to rely too heavily on the threat of additional days. The Ministry of Justice should curtail the use of additional days in all but the most serious cases.
“The overuse of adjudications is not seen as fair, it is not fair, and the imposition of additional days is very expensive and counterproductive.”