The contrast between laboratory and real-time miles-per-gallon figures has risen by 13% over the past nine years and has in turn disgruntled many of Britain's motorists, with fuel consumption (aside from price) being a major factor in the purchase of a new vehicle. 

Calls for clarity in this area were also recently aired by Chas Hallet, editor-in-chief of What Car? magazine, who recently said: 'One theme that is emerging is that lots of cars that are designed to have eco credentials are performing worse than the average. And I'm talking about cars such as a Mini Cooper diesel, and even the Toyota Prius. What we're finding with those cars is that they are performing well around town, but the economy falls apart when you take them on the motorway or at higher speeds.'

The industry has responded to criticism with claims that laboratory testing is not meant to provide exact figures for each specific driver, but more so to provide motorists with more generalised figures and for manufacturers, a platform from which to compare their figures. It is however certain that by adopting a smoother and less harsh driving style – significant economic improvements can be made on the manufacturers claimed MPG figures as has proven over many years in Britain's largest economy driving event - The MPG Marathon. 

Paul Everitt, chief executive of the Society of Motor Manufacturers and Traders, said: 'The data as it is presented is never intended to provide people with an indication of what each and every one of their real world driving miles per gallon is going to be. What it seeks to provide – and why the European commission and national governments requires us to publish it – is some kind of comparative guide.

'We have to provide some kind of laboratory test, a way of eliminating the wide range of factors that may vary on a day to day basis to ensure that we can demonstrate very clearly that we are meeting our obligations to improve the technology that we are putting on the road,' he added.

As part of the European Union's attempt to cut greenhouse gas emissions, automakers are expected to contribute by lowering the average CO2 figures across any particular vehicle range to 130g/km by 2015, or otherwise face heavy fines. 

All related documents and reports can be downloaded HERE and HERE.