MPs have branded current sentencing policy incoherent and inconsistent, and warned that it risks being driven by a misguided view of what the public want.

In a report on parliamentary scrutiny of sentencing guidelines published today, the justice committee says the five aims of sentencing set out in the Criminal Justice Act 2003 are neither coherent nor consistently applied. As a result, the public, criminal justice organisations, victims, the judiciary and government all have different expectations as to what sentencing is trying to achieve.

It says current sentencing policy, which focuses on sentence length in the misconception that the public wants longer sentences, is not ‘intelligent, appropriate or sustainable’.

The report goes on: ‘More worryingly, it may result in more people being victims of crime in the future and less confidence in the criminal justice system.’

‘We are concerned that all too often political debates about sentencing descend into a counter-productive competition as to who can appear toughest on crime, measured by sentence length,’ it says.

But it said public attitudes towards sentencing changed depending on whether people are asked abstract questions about leniency or given details of a situation and asked about the appropriate sentence.

While people may initially say they are in favour of longer sentences, when they are given the facts of a case they support sentencing at a level similar to current practice.

‘Public confidence would be better served by ensuring and then demonstrating that sentencing is effective in preventing people from being victims of crime in the future,’ says the report.

The committee said sentencing policy needs to consider not the cost of sentencing, but its cost effectiveness, measured in terms of its ability to prevent people from being victims of more crime in the future.

It noted that its ability to review sentencing guidelines was hampered by the lack of information available on the cost of different sentences and on measures of their relative effectiveness. It recommended that government urgently considers collecting and publishing such information.

Justice committee chairman Sir Alan Beith said: ‘Pursuing a policy of sending more people to jail for longer is based on the misguided conception that it will increase public confidence in sentencing when, in fact, paradoxically, it will only divert resources from the measures needed to prevent more crime, and therefore more people becoming the victims of crime.’

The committee took over responsibility for monitoring draft sentencing guidelines in May 2007. It is currently conducting an inquiry, Justice Reinvested, looking into how the finite resources available to deliver sentencing could be used to best effect to reduce re-offending.