Nearly 5,000 vehicles are untaxed in the Falmouth, Penryn and Helston areas.
And now a police operation is being planned in these areas to address the problem.
According to the DVLA data base and the Police National Computer 4,795 car owners do not have valid tax within the TR11, TR10 and TR13 postcodes.
This breaks down to TR11 – 2015 vehicles; TR10 – 952 vehicles and TR13 – 1828 vehicles.
Lists have been obtained providing the details of the vehicles, along with the name and addresses of the registered keepers.
A spokesman said: “Police are giving fair warning for all those who have not taxed their vehicles, to either do so, declare the vehicle off road by SORN declaration or scrap their vehicle.
“Anyone dealt with for failing to tax their vehicle will face prosecution, substantial fines, possible loss of the vehicle and of course the expectation that the back tax will be paid on the vehicle.”