Plainclothed traffic wardens in unmarked cars are being used to issue parking fines, trapping unsuspecting motorists.
A London council has been using the covert tactics despite the Parking and Traffic Appeals service overturning fines issued by non-uniformed officers.
Merton council is spending more than £4,000 a month on privately hired cars for traffic wardens in a move they claim is “normal practice”.
However, the Parking and Traffic Appeals Service called the methods “underhand”.
The tactics came to light following a complaint from one motorist – Derek Anderson, 54, who was issued with a £60 fine after stopping outside Raynes Park station, South London.
As he went to buy a permit two wardens pulled up behind his car in their unmarked vehicle and issued Mr Anderson with a fine.
The driver, who was not wearing a traffic warden uniform, inspected Mr Anderson’s tax disc before instructing his uniformed colleague issued a fine.
Mr Anderson, who thought the inspectors were rogue wardens, complained to the council but was told they did not have to wear uniforms as long as they were driving and didn’t issue the ticket.
He contacted the Parking and Traffic Appeals Service who overturned the penalty.
Joanne Oxlade, of the independent body, said she considered the tactics “underhand” but the council said unmarked cars were used for their officers’ “personal safety”.