Almost 16,000 days of additional imprisonment were imposed on prisoners in the East Midlands who were found to have broken prison rules last year, according to a new report.
Nationwide, the total number of additional imprisonment imposed during 2014 was almost 160,000 days - or 438 years.
The report by the Howard League for Penal Reform reveals looks at how jails in England and Wales operate disciplinary hearings, called adjudications, where allegations of rule-breaking are tried.
The hearings mainly concern disobedience, disrespect or property offences.
A prisoner found guilty at an adjudication can face punishments ranging from loss of canteen to solitary confinement and extra days of imprisonment.