Tap above to watch Ria Chatterjee's full interview with Tyrell Davis-Douglin and Jade Barnett
Police posting pictures on social media of lethal weapons taken off the streets is "fearmongering" and could even encourage people to carry knives.
The warning comes from a group of young people working with London’s Violence Reduction Unit.
They warned the police tactic could do more harm than good and urged authorities to re-examine the way they use social media.
“It’s heightening fear in our community, we’re hearing from a lot of young people that their first interaction with a zombie knife was from a Met Police website,” said Tyrell Davis-Douglin, of the VRU’s Young People’s Action Group.
He told ITV News London the images were “heightening fear” and more should be done to stop young people picking up knives.
The tactic is used by police to show the public the work being done to keep London’s streets safe and tackle knife-related crime.
But the group warned it could create a "vicious cycle" if the images make people feel unsafe.
"If I was to walk out on the street I could potentially be harmed by one of these zombie knives and it makes our young people feel unsafe,” said Jade Barnett from the VRU’s Young People’s Action Group.
"So they feel they have to have bigger knives which creates a bigger cycle," she added.
Social media posts may also be used as an intelligence source about what weapons are being carried in certain areas of the capital, the group warned.
"If they are seeing these machetes and zombie knives out being showcased in their communities the flick knives or pocket knives they were arming themselves with before it’s not adequate to protect themselves,” Tyrell Davis-Douglin said.
"So we see an increase of weapons coming into our community," he added.
Director of London’s Violence Reduction Unit, Lib Peck, said she had listened to the opinions young people.
"They have made it clear that posting images of knives seized by the police often heightens the sense of fear in our communities and could lead to young people choosing to carry a knife for their own protection," she said.
"We champion the voice of young people and that’s why we are supporting them by commissioning research to better inform the debate about knife imagery and ongoing decisions about posting images of seizures on social media," she explained.