A Birmingham project is being used as a model for young volunteers who will help police flush out shopkeepers illegally selling knives to children.
Retailers across England and Wales face a “mystery shopper” crackdown as part of the drive to tackle knife crime.
Government ministers and police chiefs want to stop dangerous weapons falling in to the hands of young people.
Ten police forces in England and Wales, covering stabbing hotspots such as London, the West Midlands, Manchester and West Yorkshire, will take part.
Volunteers aged under 18, supervised by plainclothes police officers and trading standards officials, will attempt to buy knives.
Those caught selling the potentially dangerous weapons to children face a fine of up to £5,000 and a maximum of six months in jail.