Ken Clarke has risked reigniting the row with his cabinet colleague Theresa May, saying "off the cuff" comments about sentencing are inappropriate, and declining to give a view on whether under-18s carrying a knife should carry a mandatory prison sentence.
The Home secretary Theresa May is reportedly in favour of compulsory sentences for under 18 year olds who carry knives. But Clarke said it would be a "bit of a leap".
“We have, because of the seriousness that we attach to knife crime and we think a strong message has got to be sent to people indulging in knife crime - have agreed such a mandatory sentence for adults.
"This is being tabled and the Government’s proposal. The idea that mandatory sentences for certain types of offence, to young offenders, to children, to juveniles is a bit of a leap for the British judicial system."
Theresa May clashed with Ken Clarke earlier in October during the Conservative party conference, when he accused her of making "laughable" and "childlike" comments about the Human Rights Act.
Clarke, giving evidence to the Home Affairs Select Committee on Tuesday, insisted that "sentences are far more severe than they seem to be", adding that many who complained about sentences knew little about the matter: "Half the problem is public perception," he said.
And on this August's riots, the justice secretary risked inflaming tensions with May further, saying he thought criticism of the police was easy in retrospect.
"It's usually easy in the Dog and Duck 48 hours later, to start saying what the police should have done in an unexpected and violent situation… It was totally unexpected and the scale was a surprise to all of us."
Clarke also defended previous comments about many of those involved in the disorder being part of a criminal "underclass", despite admitting not to have knowingly met a rioter. The justice secretary said he was disturbed by "irresponsible feckless reaction" from those caught up in the disorder.
"Most of these people are people who are in trouble with the police. It is re-offending. Of course the percentage is lower for the young people because some of them haven't had time to get a conviction yet… A lot of them will probably re-offend."
And he said he found the disorder disturbing: "I was slightly shocked that so many people just casually took to thieving".