The fleet software specialist points to figures from pressure group Transport and Environment suggesting that manufacturers are using a variety of techniques to artificially reduce their CO2 figures, resulting in an average 31% underreport.

T&E is backing proposed moves that would see the EU force manufacturers to adopt the World Light Vehicle Test Procedure, a new global standard for fuel and emissions measurements that is believed to be much more accurate.

Ashley Sowerby, managing director at Chevin, said: ‘We are reaching a situation where manufacturer “official” CO2 figures are really being robbed of their credibility, certainly in terms of absolute accuracy.

‘Fleets that are serious about calculating their carbon footprint in a meaningful sense need to find new ways of measuring their output. This is an important area of company vehicle activity and we should all be striving for precision.’

Sowerby reported that fleets using Chevin’s software were increasingly turning away from manufacturer CO2 figures and instead using a fuel-use based calculation as a more credible alternative.

He said: ‘We see this very much as an indication of the way in which the official figures are falling out of favour.

‘The software provides the option to work out individual vehicle/driver or global CO2 figures using either of the two methods and we are certainly seeing more fleets adopt the fuel-based approach.

‘While there can be quite an eye-watering initial increase compared to manufacturer figures, they do believe that this delivers something that is much, much close to real world CO2 output.’