Kenneth Clarke's plans to toughen up community orders by tracking offenders with high-tech ankle tags and ensuring every sentence is a punishment could increase reoffending, the Government's own impact assessment showed today.
The Ministry of Justice's initial assessment found the proposals for new intensive community punishments could increase reoffending if the essential new punitive element forces out rehabilitation requirements.
Campaigners also warned that while "tough-sounding policies and Big Brother electronics will grab headlines", there is also the "risk that politicians will confuse toughness with effectiveness".
The warnings came as the Justice Secretary outlined plans which could see every community sentence having a sanction aimed primarily at punishment, curfews backed by electronic monitoring, or a fine.
But the MoJ's impact assessment said: "Given a limit on the overall level of resources available for probation services, and the need for sentences to remain proportionate to the seriousness of the offending, delivering top end community orders may cause a number of primarily rehabilitative requirements to be substituted for primarily punitive ones.
"Evidence is unclear on the effectiveness of individual community order requirements in reducing re-offending, i.e. some requirements may be more effective at reducing re-offending than others.
"For offenders who receive intensive community punishment, there is a risk that re-offending rates may be higher than other community orders if some of the rehabilitative requirements are replaced."
But it added that the tough new sentences may also lead to "some intangible benefits arising from a greater level of public confidence in the criminal justice system, and from justice being seen to be done".
Juliet Lyon, director of the Prison Reform Trust, said: "When it comes to law and order, there is always a risk that politicians will confuse toughness with effectiveness.
"Tough-sounding policies and Big Brother electronics will grab headlines but, if you're serious about getting people to behave responsibly and determined to cut crime even further, then there's no substitute for intensive supervision of offenders by well-trained professionals, and restorative justice for victims."
Shadow justice secretary Sadiq Khan added: "This Tory led-Government's whole criminal justice strategy is built on an overriding objective to reduce prison numbers in order to fill the black hole in the budget, and these proposals appear part of this obsession.
"Community sentences should be about effectively punishing and reforming appropriate offenders.
"But managing criminals in the community is not the appropriate option for the most serious and violent offenders, and we will oppose any moves that would lead to this.
"These changes could lead to more breaches, and thus more cost as offenders are sent back to prison."
The probation union Napo also warned that tougher community sentences would only lead to a higher proportion of offenders failing to meet the requirements.
Harry Fletcher, the union's assistant general secretary, added there was also "no evidence that GPS satellite tracking will reduce crime or save costs".
Under the proposals, new GPS tags could be used to track an offender's whereabouts in a bid to reduce reoffending and act as a deterrent from further offending.
But new laws would be needed first, and the Government would need to consider the civil liberties implications and put appropriate safeguards in place, the consultation document added.
The plans could also see offenders facing driving bans and being stopped from socialising in evenings and travelling abroad under the plans designed to convince the public community sentences can be a "better deal for victims" and are not simply a "soft option".
And fines should not be reserved for the lowest level of offenders, the consultation document said.
"In the right circumstances, a heavy fine can be just as effective a punishment as a community order."
A new system of fines could also be brought in to tackle offenders who breach the terms of their sentence.
Working in a similar way to fixed penalty notices, the proposals would "create a new option for offender managers, of giving a financial penalty, without returning to court".
The proposals also include changes to make it easier for courts to strip criminals of the proceeds of crime even if they are of relatively low value - such as a wide-screen TV - in the same way they are already able to seize luxury items such as sports cars and yachts.
Mr Clarke said there was "an urgent need to reform our criminal justice system in order to improve public safety", which was paramount.