Hounslow Council face a hefty £21,000 payout to hundreds of people who were wrongly issued a penalty charge notice (PCN).
A whopping 700 car owners who received a parking ticket in the pay and display car park at Chiswick House, since May 2013, will be reimbursed.
The decision comes after the council discovered, due to an administrative error, enforcement powers were not passed to the Chiswick House Trust when they were granted a lease for the car park at the time.
A council spokespman said: “All parking enforcement undertaken by Hounslow Council at Chiswick House Trust has stopped from Wednesday (March 4).
"We are in discussions with the trust to assist them with alternative arrangements at the site.
“We regret the error and apologise to those who were issued with Penalty Charge Notices.
"We invite anyone who has been fined to contact us so we can arrange for them to receive a full refund.”
The car park, which has spaces for 60 cars including three free disabled spaces, charges from 50p for 30 minutes then two hourly rates up to £15 for all day parking.
Revenue from the parking charges contribute towards the upkeep of the car park and the care and preservation of the gardens.
Motorists who were affected are requested to provide their PCN number and evidence of payment by email to firstname.lastname@example.org. For general car park queries call 020 8583 2000.