Home detention curfew

Prisoners released three months early They must wear an electronic tag 53,813 eligible for release 2001 13,571 actually released Failure rate of 5% (breached curfew or reoffence)

Only 25% of the low-risk prisoners who would have qualified were released last year - 13,571 from a possible 53,813.

The report says: "There was much scepticism from governors and probation officers. Many see nothing in it for them except extra risk and extra work.

"As one of them put it, 'The present system is working fine for me, I've still got my job.'

"There is genuine anxiety about getting it 'wrong' and the consequences which might follow, including bad local publicity."

Under the scheme, successful applicants are let out two months early with an electronic tag which controls a curfew.

Prisons' early release of eligible inmates

The best: Ashwell, Rutland: 61% Low Newton, Durham: 60% Winson Green, Birmingham: 35% The worst: Parc, Bridgend: 3% Dartmoor: 4% Preston: 5% Woodhill, Milton Keynes: 8%

Some jails use the home detention curfew widely - such as Ashwell in Rutland which releases 61% of eligible inmates, Low Newton in Durham (60%) and Birmingham's Winson Green (35%).

Others effectively boycott it - such as Parc, at Bridgend (3%), Dartmoor (4%), Preston (5%), Bristol (6%) and Woodhill, at Milton Keynes (8%).

Yet the failure rate for the scheme has been low, with just 5% being recalled to prison for either breaching the curfew or reoffending.

The memo, from head of prisoner administration group Nick Sanderson to director general Martin Narey, adds that a "sizeable minority" of governors "objected in principle" to releasing prisoners early.

Statistics show that since the beginning of the home detention curfew in January 1999, fewer prisoners have been released on the scheme than anticipated.

They also reveal the number being released is actually falling rather than rising, despite Mr Blunkett's emphasis on the scheme's vital importance in Labour's prison policy.

Numbers in jail are at a record high

Harry Fletcher, assistant general secretary of probation union Napo, said: "The home detention curfew scheme will not resolve the prison numbers crisis unless it is properly resourced.

"Napo's analysis of last year's figures shows that three out of four eligible prisoners are not released."

He added: "The numbers released will need to double if the remorseless rise in the jail population is to be contained."

Earlier this month Mr Blunkett announced the early release date would be extended from two months to three in a bid to ease pressure on the jails.

Last Friday the number of inmates in the UK reached a record high of 69,150 - close to the system's 71,000 maximum.