According to a European research report, by the International Council on Clean Transportation (ICCT), the emissions of nitrogen oxides (NOx) in modern diesel cars are ten times greater in comparison to heavy trucks and buses.

The researchers say that the difference in the pollution levels is because heavy vehicles such as trucks and buses have to pass through strict testing conditions in the Europe Union (EU).

They suggest that similar measures have to be implemented for cars.

"It would be much better to measure the emissions of ordinary mass-production vehicles, obtained from customers who have had been driving them in an ordinary way."

Europe has registered thousands of early deaths due to Nitrogen oxides (NOx) pollution, and the UK is reported to be the most affected.

Most of the NOx pollution produced from the diesel cars is reported to be six times more than that is allowed as per the official lab-based tests.

After the Volkswagen ‘dieselgate’ scandal has surfaced, the car tests is reported to be stringent, but campaigners suspect the effectiveness of these strict reforms.

The research group from ICCT is reported to have played a key role in divulging Volkswagen’s cheating case.

The group conducted real time tests on the road and tested the NOx emission levels of cars with that of trucks.

The report released by ICCT researchers suggested that heavy vehicles in European countries like Germany and Finland have emitted 210mg of NOx/Km driven, which is less than half 500mg/km released from diesel car which Euro6 standard car.

ICCT Europe managing director Peter Mock was quoted by the guardian as saying: “In contrast, for measurement of NOx emissions from trucks and buses, mobile testing devices became mandatory in 2013.

"As a consequence, randomly selected vehicles can be tested under real-world driving conditions.

“Manufacturers will still be allowed to carefully select special prototype cars for emissions testing.

"Instead, it would be much better to measure the emissions of ordinary mass-production vehicles, obtained from customers who have had been driving them in an ordinary way.”

In September this year, a new portable devices called portable emissions measurement systems (PEMS), will be deployed on the vehicles which will be used for pollution testing purposes.

It is reported that from the same month, all the new vehicle types will require the recently finalised Real Driving Emissions (RDE) test protocol, a supplemental type-approval test which measures emissions during on-road driving within defined boundary conditions

The RDE test protocol will be fully phased in for all new registrations by September 2019.

Additionally, a new chassis dynamometer test protocol, the Worldwide Harmonised Light Vehicles Test Procedure (WLTP), will start to phase in with model year 2017 vehicles.