“On the issue of discounts, it was actually the last government that introduced a 33 per cent – a third – discount on sentences.” David Cameron, Prime Minister's Questions, 8 June 2011

Ed Miliband and David Cameron kicked off the first Prime Minister's Questions since the spring break with some testy exchanges on the issue that has dominated headlines this week: the proposals to allow judges to halve sentences for offenders that plead guilty to charges at the earliest possible opportunity.

With the press and public greeting the measures with some hostility, the Labour Leader accused the Prime Minister of performing a u-turn by rejecting his Justice Secretary's policy proposals. Mr Cameron in turn retorted that Mr Miliband was performing a volte face of his own.

To illustrate this, the Prime Minister declared that it had been the previous Labour administration that had introduced the current policy of reducing sentences by a third for those lodging early guilty pleas.

This is, however, not an entirely uncontested version of events.

Anyone leafing through a copy of the 1993 Royal Commission on Criminal Justice's report, for example, might garner an entirely different picture of the history of the practice. It noted:

“For many decades defendants who plead guilty in the Crown Court have been regarded by the Court of Appeal as usually entitled to a discount or reduction in their sentence. The usual range of discount is 25 to 30 per cent.” (p. 110, clause 41)

While this is just shy of the figure of 33 per cent referenced by the Prime Minister, it is worth bearing in mind that even today, a third is the maximum deduction offered in normal circumstances, and the Ministry of Justice itself notes that the average discount is closer to a quarter.

Indeed the Crown Prosecution Service records that Lord Taylor, delivering his verdict in the 1993 case of R v Buffrey, noted that while there was “no absolute rule as to what the discount should be, as general guidance the Court believed that something of the order of one-third would be an appropriate discount.”

This 'decades' old principle of giving offenders pleading guilty a discount when sentencing was given statutory recognition in the Criminal Justice and Public Order Act 1994, which stated:

“In determining what sentence to pass on an offender who has pleaded guilty to an offence in proceedings before that or another court a court shall take into account—

(a) the stage in the proceedings for the offence at which the offender indicated his intention to plead guilty, and

(b) the circumstances in which this indication was given.” (Section 48).

Eagle-eyed readers will notice however that there is no mention here of the size of any reduction in sentences. This was first inserted in an amendment to the Act in October 1997, with an additional subsection stating that nothing “prevents the court... from imposing any sentence which is not less than 80 per cent [of the original].” This remained in place in the Criminal Justice Act 2003.

This initial statutory offering of a 20 per cent discount was expanded upon in guidance issued in 2007 by the Sentencing Council, where the maximum reduction of one third was set:

“The level of the reduction will be gauged on a sliding scale ranging from a recommended one third (where the guilty plea was entered at the first reasonable opportunity in relation to the offence for which sentence is being imposed), reducing to a recommended one quarter (where a trial date has been set) and to a recommended one tenth (for a guilty plea entered at the ‘door of the court’ or after the trial has begun).”

So while it can be said that the one third sentencing discount received its first statutory recognition under the last Labour Government's watch, this seems to have built upon a long-standing legal tradition, which certainly was not "introduced" by Labour, as Mr Cameron claimed.

Indeed it was the last Conservative administration that first enshrined the principle of reducing sentences for those pleading guilty in law in the 1994 Criminal Justice and Public Order Act. While this left the size of the reduction to the discretion of judges, it seems it was a well-established practice to offer discounts of up to a third, a cap which was formally recognised in 2007.