Trading standards officers are investigating why the Heathrow firms charged £150 for “secure parking” while dumping the cars in “pay and display” spaces without a ticket.
The cars’ owners returned from abroad to find council wardens had issued them with as many as five tickets carrying a penalty of £120 each.
Victims claim they found out about the fines only when the council pursued them by post because the parking firms removed the tickets before returning the cars.
It is understood that the scandal has left almost 300 drivers facing combined parking fines of £33,000 for holiday breaks over the Easter weekend.
Julia O’Neill, of Lichfield, Staffs, who found one ticket on her car after returning from a two-week holiday in Vietnam with husband David, said she was “horrified”.
She added: “I wouldn’t leave my car here in the daytime, let alone the night.
I can’t believe it was left here in this unsecured car park for up to two weeks.”
Local resident Sarah Harvey, who spotted the ticket-covered cars and posted photographs on Facebook to warn people, said: “I was shocked and disgusted.
I feel sorry for the people that had been issued tickets without their knowledge and want people to be aware of the scam that was obviously happening.”
Hillingdon Council said it issued 275 tickets for illegal parking in two car parks, both 15 miles from the London airport, in the four-day spell before Easter Saturday.
Officials said drivers – who have two weeks to pay the fine at a discounted rate of £60 before it goes up to £120 – should contact trading standards if they have a query.
“We are aware of reports that some vehicles were parked in the car parks by a Heathrow parking company and not the vehicle owners,” a spokesman said.
“This is a matter we’re taking very seriously. “Our trading standards team has launched an investigation and will be contacting the people who have received the parking tickets in due course.
Everyone who receives a…