Officers are trialling new cars with cameras fitted to telescopic poles on their roofs to film drivers using mobile phones, eating or applying make-up while behind the wheel.
The Smart cars, which bear similarity to those used by Google to map the country's streets, are intended to cut the number of fatalities on Britain's roads, police say.
However, the pilot scheme has come under fire from motoring groups who claim that the tactics are an "infringement" of drivers' liberty.
Nigel Humphries, from the Association of British Drivers, said: "They might as well put something in cars to test what drivers are thinking.
"Apart from that it's going to be counterproductive. While the camera is looking into cars, other motorists could be driving erratically and causing a danger on the roads."
The scheme is being pioneered with two of the vehicles in Manchester, where distracted motorists have reportedly been involved in 406 accidents in the past two years.
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