Trading standards officers and police in Tameside are cracking down on illegal motorbikes after a teenager was seriously injured.
Two girls, aged 16 and 17, were on a quad bike when it hit parked cars on Buckton Vale Road in Stalybridge. The 17-year-old suffered a broken neck.
Police say they are increasing efforts to seize the illegal vehicles.
Trading standards officers say the main problem is cheap Chinese imports which are not safe to ride.
David Meakin, from Tameside Trading Standards, said: "The majority of the quads and bikes that we've looked at come from China.
"The ones which are produced in this country are made totally differently and are quite safe machines to ride.
"From the bikes that we've had tested, and we've had a few dozen of them, they've all proved to be extremely dangerous."
He added : "You can buy a mini motorbike for less than a £100 and quad for less than £200, so they are becoming within the reach of children, but we are appealing to parents to be very contentious and not to buy any of these vehicles."