Mr Herbert came under sustained questioning after new figures showed that just 19% of those convicted of knife crimes were going to jail. The Tory manifesto had promised ‘anyone convicted of a knife crime would receive a custodial sentence.’

He said that prison numbers would be “broadly stabilised” and that the Coalition would make prison work by increasing rehabilitation rates.

He defended draft proposals that would cut prison sentences by up to 50% if people made early guilty pleas.

Finally, Mr Herbert promised that the first elections for police chiefs would be held next year.