Think tank Civitas has distanced itself once again from the Conservative Party with an unbridled attack on Tory “justice” minister Ken Clarke’s new prisons policy which is another reversal of his party’s election manifesto.

In a press release titled “World calling Ken Clarke: prison reduces crime here too!”  Civitas, which has grown increasingly estranged from the Tory party, said that Mr Clarke was “mistaken” in thinking that crime rates had fallen as a result of fewer people going to jail.

“Kenneth Clarke, Secretary of State for Justice, has been claiming that crime fell in all developed countries in the 1990s and that it was not the result of increasing the prison population in the UK or elsewhere,” the Civitas release said.

“Most recently he repeated the claim on Newsnight on Tuesday, 30th November.

“When former Chief Constable, Tim Brain, argued that crime fell as a consequence of doubling the prison population from the mid-1990s onwards, Ken Clarke replied: 'I don't think it was caused by the prison population doubling; crime fell throughout the Western world over the years you were talking about including in places like Canada, the Netherlands and New York.'

“Ken Clarke is mistaken,” Civitas said, producing a series of charts which show that crime rates did not fall consistently across the Western world and that where they did fall, that trend was “associated with higher incarceration rates just as was observed in England and Wales.

“By contrast, significant reductions in prison populations tend to be associated with spikes in crime rates indicating that incarceration plays a role in preventing some crimes that would otherwise take place.”

All of Civitas’s statistics were taken from Eurostat, the European Union's statistics bureau. They compare the total number of crimes recorded by police with the number of individuals incarcerated for all years in which both figures are available and comparable. Charts for all countries can be found here.

Under new plans announced by Mr Clarke, thousands of criminals will not be sent to jail in an attempt to stop them re-offending.

The sentencing Green Paper currently being piloted by Mr Clarke will halve sentences for those who plead guilty and will restrict judges' powers so that indefinite sentences will be reserved for only the most serious of offenders.

Mr Clarke admitted that the shift in policy was "extremely serious” but that it would reduce crime rates, a claim to which Civitas took much offence.

The new policy also flies in the face of the Conservative Party’s election manifesto, which promised to be tough on crime and to be on the side of victims.

Under the heading “Prisons with a purpose,” the Tory manifesto said that “In the last three years, 80,000 criminals have been released early from prison because the Government failed to build enough places.

“We are determined that early release will not be introduced again, so we will redevelop the prison estate and increase capacity as necessary to stop it.”

“(These) prisoners will only be able to leave jail after their minimum sentence is served by having earned their release, not simply by right.”

The Conservative Party has already renounced another election promise on crime concerning criminals who commit knife-related offences.

The Tory manifesto promised compulsory prison for knife-crimes, a policy which was abandoned once that party came to power.