PRISONERS are being kept in jail after their sentences have finished because of mounting paperwork.

An independent watchdog has revealed dozens of inmates at Bullwood Hall, in Hockley, have been locked up beyond the point when they should have been released.

The prison, which caters exclusively for foreign men, relies on the UK Border Agency to process the necessary paperwork for them to be deported or detained again for other investigations.

But the Bullwood Hall independent monitoring board, which is responsible for overseeing conditions at the facility, said there were often delays.

Paul Norton-Ashley, the board’s chairman, said: “It is shocking that prisoners who are expecting to be released or deported at the end of their sentence are informed, often at short notice, that they will continue to be detained.

“There have been points over the last year when we have had 34 prisoners whose sentences have expired.

“The number does vary month by month, but clearly that is far too many.”

There are up to about 230 prisoners at Bullwood Hall at any point, and more than 800 passed through the prison between August 2011 and July 2012.

The vast majority are deported when their sentences are completed.

However, Mr Norton-Ashley said the process could often become derailed because of problems in the system.

Some countries, such as Somalia, have no deportation agreement with the UK, while other prisoners are required to stay in the UK because Border Agency officials have not finished investigating cases in which they are involved.

Mr Norton-Ashley said that often led to delays and prisoners being given as little as a day’s notice that they will not be released.

He said: “When they come to the prison, they are given a release date.

“Clearly, there are circumstances under which prisoners may have to be detained for longer.

“However, it is the lack of notice which they are given which is the real issue here. Telling people the day before they are due to be released is not good enough.”

A Border Agency spokesman said: "Foreign nationals who abuse the privilege of coming to the UK by breaking our laws should be removed at the earliest opportunity. We now routinely consider deportation up to 18 months before the conclusion of a sentence allowing us to remove foreign criminals more quickly. Last year we removed over 4,600 foreign criminals.

“Deportation can be delayed for many reasons, including legal challenges and a lack of co-operation by the offender and their home government in obtaining essential travel documents. In such cases an extended period of detention is sometimes needed.”