Motorists have been left fuming after discovering an unmarked police car parked on the side of a NSW highway with green P-plates attached to it.

Images of the vehicle, shared to a Facebook page titled New South Wales Authority Exposed, show a silver Ford sedan adorned with a stick-on siren, extra antennas and P-plates, according to Daily Mail.

The group labelled it "manipulative", and others questioned why an inexperienced driver would be at the wheel of a police vehicle in the first place.

One commenter suggested the car was disguised with the plates to "fool the young ones and encourage street racing".


But police have hit back and claimed the practice is "not illegal" in a comment made to Yahoo!7.

Advice from the NRMA, who say in NSW, it is not an offence for a full licence holder to display L or P plates on their vehicle while driving.

This advice did little to calm angry drivers, who likened police to Nazis and suggested they "needed shooting".

"A cop is expected to be able to safely conduct a pursuit at times," one man wrote.

"How is a P plater with three weeks or whatever driving experience going to accomplish that? There shouldn't be any cops under 25 anyway.

"They're too young to do the job properly and they don't question anything like good little Nazis."

Another wrote: "The senior cops need shooting for encouraging hoon behaviour on our roads".

One commenter had a different approach, and suggested: "I've got a really crazy idea - if you don't want to be pulled over, don't be a tosser".

It is not the first time questionable methods of disguising an undercover police car have come under fire.

One road user was dismayed to find a family-friendly SUV equipped with sirens. Photo/Facebook
One road user was dismayed to find a family-friendly SUV equipped with sirens. Photo/Facebook

Motorists have previously been outraged to discover the unmarked cars can be models other than the typical sedan.

Pictures show a silver Holden ute flashing sirens as well as a SUV, which at first glance appears to be more of a family vehicle than a police car.

One car, a green sedan, was even pictured carrying a trailer as it worked to catch law-breaking drivers.

Over the Easter long weekend, NSW police issued more than 6,000 speeding tickets, caught 199 people drink driving and attended 274 major crashes.