Blunder set to free thousands of prisoners

About 500 prisoners face immediate release from jail and several thousand are likely to be allowed out early after a blunder which could cost hundreds of thousands of pounds in compensation, it emerged last night.

The Prison Service is braced for a flood of compensation cases and the sudden release of scores of inmates. Fifty-five inmates, some believed to have been convicted of serious offences, were freed on Wednesday as an urgent review was launched by the Prison Service.

The problem has been caused by a miscalculation of the time prisoners given consecutive sentences should actually serve. Some inmates have been kept in jail for too long because the time they spent in prison waiting for their trial was not correctly deducted from their sentences. When a consecutive sentence - in which jail terms for different offences are meant to run one after the other - is given, the amount of time spent awaiting trial should be deducted from each term that goes towards making up the total amount of time to be served. However, the authorities have only been subtracting the time spent awaiting trial from the overall prison term rather than each part of it.

Probation officers estimate the error could result in up to 5,000 prisoners each year being given an average of about three months off their sentences.

The Prison Service became aware of the problem after several inmates unsuccessfully sued it for compensation. The service has put out an instruction to look at all the sentences of inmates to discover how many may be due for early release. It will have to examine about 42,000 records.Alan Walker of the Prison Service said last night: "The important thing is to make sure we recalculate those sentences as quickly as possible and... ensure that those people who should be released are released and indeed that people who are not to be released will remain in custody."