Two men pretending to be undercover cops stole a man's car after pulling him over for "hooning" in the Perth suburb of Thornlie on Friday night.
The victim pulled over and was confronted by two men claiming to be undercover police officers, who said they were seizing the man's car for hooning. One man then took the black Lancer and the other man drove off in the Commodore, leaving the victim on the side of the road.
Police have described one man as 180cm tall and the other 165cm tall, both with dark skin and dressed in casual clothes.
"Police are reminding members of the public that if approached by anyone claiming to be a police officer to ask for identification," a police spokeswoman said.
"All WA Police personnel carry an identification badge. This badge has a photograph of them, their police service number and a police badge/logo on the identification."
Anyone with information is asked to call Crime Stoppers on 1800 333 000.