Vehicle manufacturers face having to adopt more stringent emission-testing procedures as the EU Commission moves to tighten up its pollutant measuring regime in the wake of the VW defeat device scandal.

The Commission has said the current New European Driving Test (NEDC) , which came into force in 1970, is outdated and that the distance between test results and real-world driving is too wide.

Therefore from 1 September 2017 the Commission will introduce the Worldwide Harmonised Light vehicles Test Procedures (WLTP) for all new vehicle types.

The test consists of strictly fixed actions such as acceleration, braking, and idle running. The Commission claimed it is less flexible than the NEDC and eliminates a loophole that enabled manufacturers to optimise their vehicles in preparation for the test.

The Commission said the WLTP is targeted at measuring CO2, a greenhouse gas that contributes to climate change. In order to reduce emissions of nitrogen oxide (NOx), which causes air pollution, it is simultaneously launching the on-the-road Real Driving Emissions (RDE) test.

The initiative will enable national authorities to carry out spot checks on vehicles to check their emissions over a variety of roads, in a range of temperatures and while carrying a range of occupants and loads.

Critics of RDE question how accurate the tests will be if they are influenced by random factors such as driver style, weather and traffic conditions.

Vehicles that receive their NEDC certificate before 1 September 2017 may be sold until 1 September 2018.