German premium car maker Audi admitted 2.1 million of its vehicles have been equipped with the emission cheating software in the heart of the scandal that has shaken the VW group, following revelations by the US Environmental Protection Agency last week.
A member of the Volkswagen consortium, Audi said some 1.42 million of the affected vehicles with so-called EU5 engines have been sold in Western Europe, with 577,000 in Germany and 13,000 in the United States.
According to the car-maker's spokesman, models including A1, A3, A4, A5, A6, TT, Q3 and Q5 have been equipped with the emission-concealing technology, which can detect that the car is being tested and initiates action to minimise the emissions.
Research and development chiefs of Volkswagen brands Audi, Volkswagen and Porsche have been suspended today in the wake of the revelations that around 11 million cars sold around the world have been fitted with the software, known as the defeat device.
In addition to VW's CEO Martin Winterkorn, who resigned last week, further top executives are expected to leave the group as it tries to recover from the scandal, which saw its shares losing more than 30 per cent of its value over the last week.
On Sunday, German newspapers reported that Volkswagen’s own staff warned years ago about the existence of the emission-cheating technology.
Environmental group Transport & Environment said on Monday that the actual emission levels being on average 40 per cent above the laboratory results is a much wider problem not limited to Volkswagen.
The discrepancies have been found in CO2 emission levels as well as nitrogen oxide concentrations in the fumes.
Transport & Environment said that although it had no evidence to prove that other car makers are using technology similar to that of Volkswagen, further investigation is needed to find what car-makers are doing to mask emissions.
The analysis found that some new EU cars, including Mercedes, BMW and Peugeot vehicles, were using around 50 per cent more fuel than manufacturers claimed, which is directly associated with higher than official CO2 emissions.
"The Volkswagen scandal was just the tip of the iceberg," said Greg Archer, clean vehicles manager at T&E.
T&E has worked closely with the International Council on Clean Transportation, which helped to expose Volkswagen in the USA.
The analysis found the gap between official test results for CO2 and the real world rose to 40 per cent on average in 2014 from eight per cent in 2001 for EU cars.
For some models it was higher. Mercedes cars had an average gap between test and real-world performance of 48 per cent and their new A, C and E class models more than 50 per cent.
According to the study, only Japan's Toyota would have met the industry's 2015 EU target of 130 grams of CO2 per kilometre without exploiting test flexibilities, T&E said.
The target is tightened to 95 g/km by 2021 after car-makers were given an extra year to meet the new goal following an intervention by German Chancellor Angela Merkel in 2013.
T&E has worked for years to publicise the gap between lab results and real-world driving, producing an initial report in 1998.
In a statement on Monday, it said the gap was too wide to explain through well-known practices that have been tolerated in testing, such as taping up car doors to reduce wind resistance and using special driving surfaces and tyres.
The European Commission has proposed new legislation to narrow the gap and members of the European Parliament last week voted through an amendment to try to ensure it is approved on schedule and not diluted by lobbying.
Diesel car tests cheat infographic