Drivers in London are being warned to look out for unofficial congestion charge websites that charge as much as a £6 premium to pay the congestion fee to drive into central London.
Following an Advertising Standards Agency (ASA) ruling, the ASA upheld three complaints relating to paylondoncongestion.co.uk.
The ruling said this site was "likely to lead consumers to believe that the web page was an official method of paying the London congestion charge and was affiliated with Transport for London (TfL)".
TfL said the case relates to just one of a number of websites that offer to pay the congestion charge on behalf of drivers, but these sites are not official payment channels and can charge up to £6 for the service.
The TfL site does not charge to pay the congestion charge.
It is thought around 1,000 drivers per day use the unofficial congestion charge payment websites.
There have also been incidents where some of these websites have failed to pay the congestion charge, resulting in a fine for the driver.
Garrett Emmerson, TfL's chief operating officer for surface transport, said: "We welcome the ruling by the ASA and are using this opportunity to again raise awareness of these unofficial congestion charge payment sites.
"Customers should take care when paying the congestion charge online and only use the official site which is a quick and easy way to pay, and avoids any unnecessary charges.
"We are doing as much as we can to minimise the risk of unofficial websites or adverts misleading customers into paying more than they need to, including talking to trading standards and the Office of Fair Trading and calling on search engine providers like Google to do their bit to put a stop to this."