There will also be a small unit for foreign prisoners
A Kent jail is to become a unit for treating sex offenders, the Prison Service has confirmed.
HMP Maidstone, which houses about 480 inmates, will house sex offenders almost exclusively by the end of June.
There will also be a unit for a small number of foreign prisoners awaiting removal by the UK Border Agency (UKBA).
Other offenders currently at Maidstone will move to other prisons over the next five months as it expands its treatment programme for sex offenders.
A Prison Service spokesperson said: "It is anticipated that by 30 June 2009, apart from a small population of foreign national prisoners, Maidstone will be dedicated to the delivery of these programmes.
"The dedicated foreign national prisoner unit will mean that the UKBA will be able to process removal proceedings more quickly."
In 2007, Maidstone was criticised by the prisons inspectorate over a drugs culture, dirty and untidy facilities and a lack of training opportunities for inmates.