Independent testing by the UK government had found that Volkswagen is the only manufacturer guilty of using defeat devices in emissions tests.

The Department for Transport yesterday released the results of a £1 million inquiry and stated that it didn’t uncover evidence of any other manufacturer using similar methods to rig its emissions tests.

Patrick McLoughlin, Secretary of State for Transport, said: “Our tests published today have not detected evidence of manipulation of emissions lab tests as used by the VW Group by any other car manufacturer.”

However, the government did highlight the gap between official tests undertaken by manufacturers in laboratory conditions and real-world emissions figures.

The tests were carried out on a total of 37 different types of vehicles in the UK over a six-month period, which the government says is a sample representative of the UK’s top-selling diesel cars.

'Higher emissions in real world'

Exhaust emissions tests were performed on the vehicles under laboratory conditions, but also on a closed test track and during typical everyday road use as well to determine more accurate readings.

From next year, the government said that vehicles will have to meet emissions limits according to real-world tests in order to improve consumer confidence in car manufacturers.

Mr McLoughlin said: “The tests do show the widespread use of engine management systems to prevent engine damage which can lead to higher emissions in real world temperature conditions cooler than those in the approved lab test.

“The UK has been leading in Europe in pushing for real world emissions tests which will address this problem. Real world tests will be introduced next year to reduce harmful emissions, improve air quality and give consumers confidence in the performance of their cars.”

He added: “Following the Volkswagen emissions scandal the whole of the automotive industry must work hard to restore public trust by being transparent about the systems they employ and advancing plans for introducing cleaner engine technology.”