More needs to be done to tackle prisoners' offending at the country's first jail to hold only foreign inmates, regardless of whether they are to be deported or not, the Chief Inspector of Prisons has said.
There were no offending behaviour programmes at HMP Canterbury in Kent because of a belief that there was little benefit when offenders were to be sent back to their home country, a report said.
Nick Hardwick said that whether prisoners were returning to their own country or freed back into the community in the UK, they should still receive support to cut their risk of reoffending and help them resettle.
Apart from the failure to deal with inmates' offending behaviour, the inspectors' report found that Category C training prison HMP Canterbury, which in 2006 became the country's first jail to hold only foreign men, was generally well-run.
They also described offender management as "poor", with some high-risk offenders wrongly identified as low-risk and those correctly deemed as high-risk were sometimes ignored by offender managers in the community.
The report also highlighted flaws in the UK Border Agency, with inspectors saying that its unpredictable processes made it "impossible" to tell who would be deported, who would be transferred and who would be freed until just before the end of sentence.
The report noted: "Inspectors found that 20% of prisoners were released into the UK and an additional unknown number were released after transfer to immigration removal centres.
"Whether prisoners were returning to their own country or being released into the community here, they should have received support to reduce the risk that they would reoffend and to help them resettle successfully, both in their own interests and that of the communities to which they returned."
Inspectors noted that prisoners generally felt safe, security was effective and there was little evidence of illegal drug use.
Given the age of the jail, which dates from 1808, the residential areas were well-maintained, although cramped.
Staff and prisoner relationships were said to be good, and most inmates were usefully occupied, and the quality of the education in some areas was deemed to be "outstanding".
Mr Hardwick said: "HMP Canterbury is a generally safe, decent and well-run prison, where good efforts have been made to keep prisoners purposefully occupied.
"However, prisoners must also be prepared for the day they will leave its confines.
"The National Offender Management Service must ensure that offending behaviour and resettlement needs are addressed for everyone, as happens in other prisons, regardless of final destination or nationality."
Michael Spurr, chief executive officer of the National Offender Management Service (NOMS), said: "I am pleased that the Chief Inspector has recognised the good work being undertaken at Canterbury, despite the complex and specific needs of the prisoners it holds.
"Our priority is to facilitate the return of those prisoners whom UKBA take deportation action against.
"We will consider the report's findings and consider how best to support the resettlement of prisoners against whom no action is taken and who remain in the country on release.
"Training has already been identified and provided for offender supervisors and a new model has been introduced to assess and prioritise risk."