With CO2 emissions exceeding official measures by an average of 42%, millions of vehicles have been placed in tax bands that do not reflect their true levels of pollution, according to new research published on Saturday.

Since 2001, UK vehicle excise duty has been based on carbon emissions. Cars registered before April 2017 and producing less than 100g of CO2 per km are exempt, with the rate rising to £535 for the most polluting cars.

Analysis for the Green party in Europe shows that car taxes would have been more than €10bn higher across 11 EU countries last year, with the UK one of the main losers due to its large car fleet and graded tax system.

The report estimated a loss of more than £2bn in the UK in 2016, based only on new vehicles registered since 2010, which make up around half of the cars now on the road.

One of the authors, Matthias Runkel of Green Budget Germany, said evidence showed a greater divergence in lab results and actual emissions after 2010, but including older vehicles the true loss to the exchequer was likely to be far higher.

Molly Scott Cato, Green spokeswoman on tax justice in the European parliament, said: “Taxation based on the polluter pays principle has the potential to gear up the transition to a low carbon economy.

“Instead, the shocking loss in potential tax revenue from cars has been matched by an air pollution health crisis in our cities and increasing CO2 emissions driving climate breakdown.”

Further calls for road tax to better reflect pollution have come this week after independent testing revealed some new diesel models, certified as Euro 6 compliant, emit more than 12 times the legal limit of NOx in real-world conditions. Fiat 500X, Nissan Juke and Renault Megane models were all graded among the worst polluters in tests conducted by Emissions Analytics.

However, testers found that other diesels – including BMW 5 Series, Mercedes E Class, Audi Q2, Seat Alhambra and VW Golf models – beat some new petrol cars. They emitted less than 80mg/km of NOx pollution in real-world tests, lending partial support to manufacturers’ claims that the newest diesel cars are the cleanest ever.

Industry body SMMT has warned that more pollution could be a consequence if consumers hold back from buying new cars.

Tax changes, following concern over public health and air quality, in the wake of the VW scandal, have seen diesel sales plummet. All new diesels will be placed in a higher tax band from April, before a real-world driving emissions certification comes into force in 2020.

Nick Molden, the chief executive of Emissions Analytics, said: “The most efficient diesel engines continue to improve while some of the worst remain on the market, meaning the confusion for consumers increases rather than diminishes.

“The danger is that motorists who bought genuinely clean diesels – together with the manufacturers who made them – suffer the consequences of the general confusion and loss of confidence.”

He added that both CO2 and particulate pollution could rise as a result.

Gwyn Topham 

This article first appeared on the Guardian

edie is part of the Guardian Environment Network

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