Some drivers have said they have been asked to pay more than £500 in fines despite having thought they were in the clear.
"Let’s just say I felt quite ill and quite faint afterwards because I thought I’d done the right thing by paying and then found out I hadn’t paid at all,” Bobby Sharp - a motorist to have been caught out -told the BBC on Tuesday.
"TfL has not made it easy. Their official site is not user-friendly, whereas the scammers’ was so easy, and I thought ‘Well, I don’t know why I was so worried about this’.
"The whole process was frustrating once I had to do it properly."
How do Ulez scams work?
Drivers of the most polluting cars are required to pay £12.50 a day for driving through the capital’s boroughs - although the M25 is not included.
The charge can be paid up to three days after travel by phone or on the TfL website - but users have been hit by the scams after Google results revealed bogus Ulez results.
This is then seeing a £180 fine charged to the unsuspecting users, although this can go down to just £90 if paid within two weeks.
Among the unlucky drivers was David Kenna who told the BBC: "The thing that annoyed us particularly was TfL had no sympathy whatsoever. They couldn’t give a monkeys, basically. Nobody ever contacted us to ask about this scamming site.”
The Ulez boundary expanded from London’s centre to the whole city on August 29.
How to avoid a Ulez scam
To pay on the official website for Ulez payment, click here.
Make sure the address begins with tfl.gov.uk.
A quick Google search by the reporter did not find any scam results - however, these are likely to spring up and be shut down at a moment’s notice.
What has TfL said?
Transport for London has said it is working with search engines to remove scam Ulez results.
A TfL spokesperson told the BBC: "We are sorry to hear of any customers that may have been caught out in this way.
"TfL has no association with third-party organisations that process charges, and we work proactively with search engine companies such as Google, as well as with Advertising Standards and Trading Standards, to remove them entirely from the internet.
"We advise drivers who have been impacted by overcharging by a third-party site to contact Trading Standards.”