PRISONERS who broke jail rules did an extra 2,152 days in Winchester prison last year.
That is up from 1,540 extra days, the Howard League for Penal Reform said.
Inmates serving determinate sentences can be handed longer in prison for causing trouble.
But the charity said any jail with lots more days imposed should be cause for alarm.
Frances Crook, Chief Executive of the Howard League for Penal Reform, said: ‘The explosion in the use of additional days of imprisonment has been a catastrophe for the prison system. Rather than solving problems, it has created new ones – piling more pressure on the prison population and worsening overcrowding, which in turn leads to more drug abuse and violence.
‘These figures illustrate the urgent need for reform. We need to see a culture change in jails, from top to bottom. A prison that resorts again and again to further punishment is an unhealthy prison.
‘Scrapping the imposition of additional days would make prisons safer.’