Anti-pollution group Transport & Environment (T&E) claims the difference between what cars really emit and what they are officially measured as emitting has grown to nearly a quarter.

In a strongly worded statement it says this is caused by carmakers’ manipulation of testing procedures, which it describes as ‘not fit for purpose’.

T&E commissioned Dutch consultancy TNO to measure fuel consumption and CO2 emissions on six standard new cars. On average, TNO found the results of their tests to be 23% higher than the official figures.

The findings were published in a report called ‘Mind the Gap!’ which outlines techniques to ‘creatively reinterpret test procedures’, including:

• Taping over cracks around doors
• Using special lubricants
• Testing at altitude and on super-slick test tracks

T&E cars officer Greg Archer said: “Consumers’ trust in official information and regulation is breaking down, because what it really costs to run a car is a quarter more than the official test results say.”