The Luther star, 51, has launched the Don’t Stop Your Future campaign calling for machetes and so-called zombie knives to be banned with immediate effect.
The actor was asked if police tactics such as stop and search work.
He said: “There are hard facts that stop and search may do some help but it’s not eradicating the issue.
“We need to think a little deeper than that. It’s not just about stop and search…Some kids are carrying these knives because they’re scared and some are carrying knives because it makes them feel more protected.
“Stop and search will do some work but we need to kind of pull the onion back a little further and figure out what are the roots.”
Police can stop and search people and vehicles, without suspicion, for offensive weapons or “instruments” considered dangerous in specific neighbourhoods for set periods.
Idris said the focus should be on how young people can get weapons, saying tech firms should be held accountable for knife imagery on mobile phones.
He said: “I can pick up a phone right now, type in knives and I’ll get inundated with adverts for them. We should find a way to deter tech companies.”
The actor was among campaigners in Parliament Square, Central London, yesterday morning who laid out clothes to represent those killed by knives on our streets.
The Home Office previously said tougher measures on machetes and zombie knives would be introduced.
Machetes and knives meant to intimidate and threaten will be made illegal. The maximum penalty for importing, manufacturing, possession and sale will be two years.
But passing the new legislation has been slow and several high-profile crimes, like the killing of schoolgirl Elianne Andam, have happened since.
The 15-year-old was stabbed to death in Croydon, South London, in September with what is believed to be a zombie knife. A boy of 17 has been charged with murder.
Idris, who is releasing a song called Knives Down, said: “I can’t stay silent as more young lives are lost to these brutal and heartless crimes. As school returns, too many young people will not be joining their classmates and too many grieving families have lost a young person they love in recent years.
“Young people are our future – their potential deserves to be met, not taken away by violence.”
Don’t Stop Your Future has produced a series of billboards highlighting the risk across the country.
At the launch was Yemi Hughes, who held the clothes her son Andre Aderemi, 19, wore when he was stabbed to death in Croydon in 2016.
No10 said knife crime is down 7% but added: “We do want to do more. It’s welcome that Idris Elba and others continue to shine a light on this important issue.”
A spokesman said: “We are using the Criminal Justice Bill and other means to give police more powers to act in this space including seizing dangerous weapons.”
