A 26-year-old man has been arrested on suspicion of impersonating a police officer after an off-duty police officer was pulled over in Craigavon.
He was stopped on the M1 at about 01:00 BST on Wednesday.
The officer stopped his vehicle on the hard shoulder.
The driver of the “police car”, an unmarked Skoda Superb which was fitted with blue flashing lights, showed him an ID card and said the off-duty officer had been speeding.
Police said the off-duty officer saw the ID card was not a legitimate Police Service of Northern Ireland (PSNI) warrant card and then got out his car and challenged the man.
The man immediately drove off at speed.
A suspect was later found in Bluestone Hall in Craigavon and was arrested.
Ch Insp Barney O’Connor said it was a “concerning” incident and that the PSNI would be keen to hear from anyone who believes they may have encountered this man while he has been pretending to be a police officer.
“We believe it is possible that this is not the first occasion he has done this and he was simply unlucky to have pulled over a police officer,” he said.
The man is described as white, approximately 5′ 9″ tall, medium build with brown hair and blue eyes and spoke with a Polish accent.