A BBC Watchdog investigation into Audi has discovered widespread lying about the safety testing of their vehicles.
Undercover researchers witnessed nine out of 10 dealers from around the country falsely claim the Audi A5 was Euro NCAP safety tested.
But the A5 - as well as the A7, A8 and R8 - are not tested. Audi's UK head office falsely claimed that the entire Audi range was Euro NCAP safety tested.
Audi UK said there had not been any deliberate intent to mislead.
Six of the dealers claimed the Audi A5 had achieved the maximum five stars.
The Euro NCAP (New Car Assessment Programme) safety tests are funded by various European governments and motoring bodies. Their ratings are frequently cited by manufacturers as a gold standard of safety.
Popular models are either selected for testing by the organisation themselves, or car manufacturers can pay to get their models tested.
But there is no legal requirement for cars to be Euro NCAP tested.
The issue was brought to the BBC's attention by Daniel Jenkins, owner of a high-end car rental business.
He bought an R8 supercar in December 2012 after a local Audi dealer advised him it had a five-star Euro NCAP safety rating.
A few months later Mr Jenkins's father, Paul, was involved in an accident while driving it.
Despite the R8's safety performance not being responsible for the accident, Mr Jenkins decided to research the official safety credentials of the car, so he contacted multiple dealerships.
He told Watchdog: "Forty-eight of the 50 dealers I spoke to told me directly that it had been put through the Euro NCAP programme and it had a five-star rating."
Mr Jenkins then contacted Audi head office about the dealers' lies. In December 2013 Audi responded, telling him they were taking his allegations seriously - five months before the Watchdog investigation.
When told about Watchdog's findings, Tim Shallcross, a spokesman from the Institute of Advanced Motorists said: "I find it incredible… that a company of the reputation of Audi, and their parent group, the Volkswagen Group can allow their product to be misrepresented so badly in that way.
"Nobody's saying the cars aren't safe, but if they haven't been tested... to say that they have, that's outrageous."
'No intent to mislead'
NCAP spokesman Aled Williams said: "Most of the car companies that we deal with have large marketing departments. These marketing departments understand full well what the safety ratings mean, and it's disappointing to find out that that information is not being filtered down to the point where it matters most… where people are selling cars to consumers.
"Euro NCAP is not a regulatory body, we have no legislative powers.
"All we can do is speak to Audi at a high level and try to encourage them to make sure that the dealers are better informed and better trained."
An Audi spokesman said: "Audi UK wishes to emphasise that there has not been any deliberate intent to mislead on the part of its customer-facing staff where the Euro NCAP safety test performance of the Audi model range is concerned."
"Audi vehicles are engineered to exceed international motor vehicle safety standards. The company fully supports Euro NCAP's efforts to improve vehicle safety.
"We are now aware that our sales and customer service staff must be more conversant with the Euro NCAP safety test register and specifically the Audi models included on it.
"We have already begun a comprehensive and far-reaching review of all of our communications and training procedures to ensure accuracy of information on test data provided to our customers."