Knife carriers will still be let off with a fine, admits Jack Straw

Under the rules, issued by the Sentencing Guidelines Council, magistrates will be told that the starting penalty for carrying a blade in public should be a fine - even though the maximum punishment is four years in jail.

Last week Home Office minister Tony McNulty backed anti-knife campaigners and opposition politicians who have attacked the new guidelines.

But Justice Secretary Mr Straw, who has ultimate responsibility for the guidelines council, conceded he was powerless to stop the rules from taking effect on 4 August.

At a Westminster news conference, he promised "talks" on the issue, but was unable to give any commitment that a proper review - which could lead to a stricter sentencing approach - would be carried out. Mr Straw said: "I am aware of what Tony McNulty said on this and will be having talks with other ministers about this. But they will be coming in on 4 August. We can't stop that."

Mr Straw's admission is likely to prompt claims that ministers' rhetoric on knife crime is not being matched by action. It follows complaints about the large number of knife offenders who escape with light sentences or cautions. Latest official statistics show fewer than one in five of those caught with a blade in public get a custodial sentence, despite the maximum penalty doubling from two to four years recently. Only a handful get more than a few months in jail.

Gordon Brown has said he wants a new "presumption to prosecute" for anyone found carrying a blade longer than three inches.

But today, Conservative leader David Cameron announced his party would adopt a policy under which any offender caught on the streets with a knife would face jail. Everyone carrying a blade without a reasonable excuse would be prosecuted, and those convicted would be expected to get a custodial sentence.

More than a decade after John Major's "back to basics" crusade, Mr Cameron said it was time to talk again about "right and wrong", and he linked teenage murders to Britain's wider moral decay.

In Glasgow East, where Mr Brown is facing a by-election this month, Mr Cameron said the poll would become the "broken society by-election". He added: "We are living in a country where being stabbed is no longer the dark makebelieve of crime fiction but the dreadful reality of our children's daily lives."

Lack of school discipline and parental control, and the benefits culture, had combined to create a country where no one took any responsibility. "In order to avoid injury to people's feelings, in order to avoid appearing judgmental, we have failed to say what needs to be said.

"We have seen a decades-long erosion of responsibility, of social virtue, of self-discipline, respect for others, deferring gratification instead of instant gratification. Instead we prefer moral neutrality, a refusal to make judgments about what is good and bad behaviour, right and wrong behaviour."

Mr Cameron said it was time to make judgments to say people were wrong to eat too much and not take exercise, wrong to say marriage didn't matter, and wrong not to bring up children properly.

"Back to basics" hit the buffers in the Nineties when several Tory MPs were embroiled in financial and sexual scandals. But Mr Cameron said: "Bad. Good. Right. Wrong ... Of course, as soon as a politician says this there is a clamour: 'But what about all of you?'

"Yes, we are human, flawed and frequently screw up. But if the result of this is a stultifying silence about things that really matter, we redouble the failure.

"There is a danger of becoming quite literally a de-moralised society, where nobody will tell the truth any more about what is good and bad, right and wrong. That is why children are growing up without boundaries, thinking they can do as they please, and why no adult will intervene to stop them - including, often, their parents."

Mr Cameron refused to apologise for his "hug a hoodie" approach, saying Britain had the highest level of family breakdown and teen pregnancy in Europe.

The Tories' Knife Crime Action Plan stops short of a mandatory jail term but the presumption should be that offenders would go to prison. The minimum sentence would be a community penalty with the offender wearing a high-visibility uniform.

The Tories are also proposing to sell off Victorian prisons such as Wormwood Scrubs and use the cash to build new jails. They want to end the couple penalty in benefit claims so families no longer have the incentive to live apart.

Headteachers will have the automatic right to exclude pupils without the right of appeal to an independent panel.