Prisoners will divide their time between jail and the community

The jails will house offenders who would normally be given a prison sentence but are not considered high enough risk for immediate jail.

They will spend either weekends or weekdays there, and the rest of their time living in the community.

New facilities at two prisons in Preston and Lincoln will house the "intermittent custody" prisoners.

While in the community the offenders will be under the supervision of probation officers, either working, looking for a job or doing unpaid community work.

Intermittent custody will focus on reducing re-offending by reducing the negative impact of short custodial sentences. David Blunkett Home Secretary

If behaviour is not up to scratch they may be sent to jail full time.

Th units at Kirkam and Morton Hall prisons which will open on Monday have been purpose-built.

Home Secretary David Blunkett said: "Intermittent custody can play a key role by punishing offenders at the same time as ensuring they undertake programmes to address their behaviour and make reparation to the community."

Prisons minister Paul Goggins said the policy would focus on reducing re-offending.

"Many offenders serving short sentences lose their jobs and homes, and their family suffer from the separation, but the Prison Service do not have long enough to work constructively with the prisoner."

Pilot magistrates courts will have the power to impose an overall sentence of up to 26 weeks for a single offence, including up to 45 custodial days.

In the Crown Court, the sentence for a single offence will be up to 51 weeks including a maximum prison element of 90 days.

For most offenders community sentences are a far better option than either part-time or full-time prison, as they are much more likely to change attitudes to offending Paul Cavadino, Nacro

The Probation Service will assess offenders' suitability for the new scheme.

As well as looking at the degree of risk posed by the offender, they will consider whether issues such as drug or alcohol abuse make them unsuitable for part-time custody.

Chief executive of Nacro, the crime reduction charity, Paul Cavadino, generally backed the initiative but warned there was a real risk that courts could misuse intermittent custody for offenders who would not otherwise have gone to prison.

"If this happens, it will simply increase the total jail population and provide no relief for an overstretched prison system."

He added: "For most offenders community sentences are a far better option than either part-time or full-time prison, as they are much more likely to change attitudes to offending."