A driver was conned out of £400 by two people posing as police officers who said he had to be fined for being outside during the lockdown.
The man was pulled over in Chippenham, Wiltshire, by a black BMW car that flashed its lights and indicated for him to pull over.
Wiltshire Police said a man and woman got out the BMW and said they were undercover officers.
The victim paid the money but was given no paperwork.
A police spokesman said officers were trying to identify the fraudsters and "the public should understand this is not the sort of work undercover officers would do".
"Any vehicle stops conducted by officers in relation to Covid-19 restrictions will be high visibility, and fines will be issued as a last resort," they added.
"Members of the public are also within their rights to ask to see a police officer's warrant card if they have any concerns about their identity."