How much fuel does your car REALLY guzzle? Mercedes tops league of shame with their vehicles using 54 per cent more fuel on the road than they claim

German car giants Mercedes have been left red-faced again as it emerged the average gap between real-world fuel consumption and lab results for their cars is 54 percent.

The Mercedes A and E classes are burning 56 percent more fuel on the road that is claimed in their sales brochures, according to a report by the Transport and Environment's Mind the Gap, after Emission Analytics found their diesel engines emitted four times the legal limit for nitrogen oxide last year. 

Figures show industry-wide statistics are also still skewed with the average gap for cars in Europe at 42 percent, costing drivers around £460 extra a year at the pump.

Mercedes C class, pictured, are burning 54 percent more fuel than the marketing information.

Mercedes is the worst-performing manufacturer, with the C class burning 54 percent more fuel than advertised, compared to the VW Passat, which is measured at 46 percent. 

The fuel efficiency tests are conducted in the laboratory with many loopholes and flexibilities and are prone to extensive manipulation. 

Greg Archer, clean vehicles director of Transport and Environment, said: 'Cars that burn 50% more fuel than advertised are deceiving consumers and cheating environmental rules. 

'Unless we want the Americans do Europe's job again, the commission and national vehicle approval authorities must investigate Mercedes and Audi and determine if they are using devices to defeat the test.'

Last year, Mercedes, Honda, Mazda and Mitsubishi were found to be producing cars which emitted far more pollution on the road than they do in a lab.

Mercedes was also accused in a lawsuit back in February of selling diesel cars in the US that spew excess emissions of nitrogen oxide and concealing the mechanism from regulators. 

Representations by Mercedes that its BlueTEC diesel technology is the world's 'cleanest' are 'deceptive and false,' said the suit.

Lawyers likened the issue at Mercedes to the scandal which has enveloped German rival Volkswagen, which has faced a torrent of criticism and government probes after acknowledging that it installed 'defeat devices' to flout emissions rules on some 11 million cars.

A Mercedes spokesman said there was no basis for the suit.

'Currently we are reviewing the documents and we will defend ourselves,' said a Mercedes spokesman. 'We believe the complaint is without merit.'

BMW is matching the industry-wide figure of the gap between real-life fuel consumption and lab tests with the gap being more than 40 percent.

The Volkswagen Passat, the Mercedes C class' equivalent, is running at 42 percent more than advertised.

The average gap across all brands in Europe is quickly growing, jumping from 28 percent in 2012 to 42 percent last year. 

The gap was 14 percent a decade ago. 

Audi is the second worst brand with an average gap of 49 percent. 

In general, most car brands have an average gap higher than 40 percent with Peugeot at 45 percent, Toyota at 43 percent and Volkswagen at 40 percent.

The exception is Fiat, which is still operating at 35 percent higher than advertised.

Distorted test results deceive European drivers whose cars consume much more fuel than is promised in marketing materials. 

Audi is the second-worst performing manufacturer, according to the study by Transport and Environment's Mind the Gap.

Mr Archer added: 'There has been no improvement in the average efficiency of new cars on the road for four years because carmakers manipulate tests to achieve their CO2 targets instead of designing the car to be efficient on the road.

'As a result, drivers are being tricked and forced to buy more fuel; governments defrauded of tax revenues; and climate targets undermined. 

'More than a year after the Dieselgate broke, we urge regulators in Berlin and the European Commission to get to the bottom of this Autogate.'