New laws to crack down on knife crime could cause increased hostility among young people, the Children's Commissioner for England has said.
Sir Al Aynsley-Green called for more research into the effects of increased police powers.
New measures are being used by police to search for knives using hand-held and walk-through metal detectors.
The police say the powers are not aimed at victimising young people but are designed to keep them safe.
Sir Al said on BBC Breakfast: "There is a balance here. On the one hand for young people to feel safer by having the presence of the police - but on the other hand making sure the new powers don't create further antagonism by increased stopping and searching.
"These are very contentious and I certainly support the case for much more research on the effects of these policies on them."
Sir Al said young people should be seen as part of the solution rather than part of the problem.
Metropolitan Police Deputy Commissioner Rose Fitzpatrick said officers' work was intended to make young people feel safer, as well as actually making them safer.
The new powers follow a rise in fatal knife attacks in London
"The work we are doing in London in particular is working alongside communities to do robust stop-and-search operations using knife arches and search wands where intelligence tells us that there is the most likelihood that people are carrying knives and weapons," she said.
"That is not aimed at victimising young people; it's aimed at keeping them safe."
Under the Metropolitan Police's plans announced this month, officers can search people without reasonable suspicion under Section 60 of the Public Order Act.
The move followed a rise in fatal knife attacks in London.
The first team of 15 officers has already been deployed to an unidentified London borough.
Another five to 10 teams will take to the capital over the next 10 days, and will target areas where intelligence suggests youths are more likely to carry weapons.
Youth worker Nathan John said of young knife-carriers: "If they don't carry a knife they know someone else is. They can't be defenceless.
The kids are carrying knives because they don't feel safe
Camila Batmanghelidjh Kids Company
"I know that's a problem - but until we make them all realise they have to get rid of all their guns and knives we wont find a solution to this problem."
Gerald Pontet, the guardian of 14-year-old Nuttawut Meechao, who was stabbed to death near Finchampstead in Berkshire in 2005 by another teenager, told the BBC News website he was "appalled" at Sir Al's comments.
"Sir Al's concern is for the effect on youngsters and their relationship with authority," Mr Pontet said. "As parents our concern is what our, or other youngsters are up to - are they safe to be out and about and are they going to come home safely?
"To say that our children 'should be part of the solution not part of the problem', Sir Al is using meaningless doublespeak, and if this is his position, he has no real contribution to make."
Camila Batmanghelidjh, founder of children's support charity Kids Company, told the BBC that stop-and-search did not address the "core problems".
"Violence is a bit like a virus," she said. "It's spreading amongst children and children are feeling really unsafe, and the reason is the failure of adults to create structures that protect children.
"So what's the point of just searching the children and not solving the core problems? The kids are carrying knives because they don't feel safe."
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