Gordon Brown today urged prosecutors to take more 16 and 17-year-olds to court if they are caught carrying a knife.
At a breakfast meeting, Mr Brown urged that a "presumption to prosecute" in cases of knife crime is applied more widely.
Currently, it is only the case in certain hot-spots and then only among those over 18 but the Prime Minister wants it to be rolled out nationally and to 16 and 17-year-olds.
At today's meeting the Director of Public Prosecutions, Sir Ken Macdonald QC, told Mr Brown: "When people come to us their expectation is a prosecution will follow.
"What we are proposing is that if people are carrying a knife and are prosecuted for other offences, they will be prosecuted for the knife too.
"We have set out some further guidance that the public interest is in favour of prosecution.
"It has become fashionable (to carry a knife). What we want people to understand is they put themselves at risk carrying these sorts of weapons."
After the 40-minute meeting concluded, the Prime Minister said: "Carrying a knife is completely unacceptable. When any young person or teenager who is encouraged to carry a knife is not making themselves safer, they are all making it more likely crimes are committed.
"We have got to make sure if a young person is carrying a knife, there is a message they will end up in court.
"They are putting other children and young people at risk."
Also at the meeting were Home Secretary Jacqui Smith, Justice Secretary Jack Straw, Attorney-General Baroness Scotland and Sussex chief constable Ken Jones, who is the president of the Association of Chief Police Officers.
Yesterday Mr Brown told the House of Commons that parents also needed to be responsible for telling their children not to carry knives.
He told MPs: "Every parent will want their teenage sons and daughters not only to be safe but to feel safe in our neighbourhoods.
"That's why knives are unacceptable and we've got to do everything in our power to deter them."
On Tuesday Ms Smith outlined measures to tackle knife crime, including an advertising campaign aimed at deterring young people from carrying knives. Ms Smith said information would be provided to help parents broach the subject.
Last week Metropolitan Police Commissioner Sir Ian Blair, who did not attend today's meeting, pledged to continue a controversial crackdown which has seen police in London using section 60 powers to stop and search people even if they have no suspicion that they are carrying a knife.
Critics have said that continued use of the powers could aggravate police relations with the community.
Sir Ian said the crackdown, called Operation Blunt, will stop when murders reduce.
Sixteen teenagers have been killed so far this year in the capital.
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