Fifteen women’s jails in England and Wales would close and be replaced with small custodial units in the biggest prison shake-up under consideration by the Justice Ministry.

The plan also involves sweeping changes to the current classification of jails, including the development of a federal system holding only high-risk offenders with other criminals in so-called community prisons, The Times has learnt.

Many short-term prisoners would be held in open community prisons rather than in closed jails, which would offer them detoxification treatment and help with resettlement in the community.

The proposals also recommend that remand prisoners be held within dedicated units in community jails, where they would be managed separately from other inmates.

The outline for the biggest restructuring of the jail system in decades is part of a review of prisons being conducted by Lord Carter of Coles for the ministry.

His findings, expected to be published within the next few weeks, are part of the Government’s attempts to get a grip on the prison numbers crisis.But last night prison governors and a criminal justice think-tank said attempts to restructure the prison system were doomed to fail without an easing of population pressure and an input of extra cash.

Charles Bushell, general secretary of the Prison Governors’ Association, said: “These are interesting and innovative plans. Unfortunately at the moment the Prison Service is struggling simply to contain the ever-growing numbers who are sent to prison.

“At a time when every place is at a premium, it is difficult to see how such an ambitious programme can be brought into place and it will require considerable additional resources.”

Enver Solomon, deputy director of the Centre for Crime and Justice Studies at King’s College London, said: “Any proposed reconfiguration of the prison estate is effectively meaningless while the prison service is in a state of crisis dealing with constant overcrowding. What is needed is a radical review of the sentencing framework.”

The proposals are contained in an interim report prepared by the National Offender Management Service for a workshop held last week on the Carter Review. Under the plans the 15 women’s jails would be replaced by smaller units run as family units holding up to about 20 women. Only women jailed for long periods would be in the unit.

The document does not say what would happen to the existing women’s prisons but some, such as Holloway in North London, could be sold for housing, while others could hold men.

The paper, seen by The Times, outlines a reshaping of the existing system into federal and community prisons rather than the current four-tier top-security, training, local and open categories of jails. It also calls for criminals held in the new-style community prisons to be segregated on the basis of their risk of harm to the public and how close they are to the end of their sentences.

“The very small percentage of prisoners assessed as posing high risk of serious harm to the public to be placed in a dedicated ‘federal’ estate, the rest placed in closed or open community prisons,” the document said.

This proposal suggests that the existing high-security prison system would be slimmed down. It would also end the current practice where some top-security jails hold both high-risk offenders and less dangerous criminals. The report added: “Local community prisons to become urban resettlement prisons whilst other closed establishments focus on risk reduction, including for indeterminate sentenced offenders.”

Short sentence prisoners, who are not a risk to the public, and those coming towards the end of long jail terms would be put in “open community prisons”, which would provide detoxification facilities. It proposes that women are held in smaller local units as recommended in a review published this year.

There are presently 4,408 women in jail, including 923 on remand, 504 serving less than six months, 206 six to twelve months, 1,147 more than four years and 311 indeterminate sentences.

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