Laboratory tests could be underestimating the amount of nitrogen oxide produced by diesel cars by as much as 50%, new research has claimed.

According to the research, diesel vehicles emitted 13.2 million tons of nitrogen oxide under real-world driving conditions, compared to 8.6 million tons under official laboratory tests.

The research estimated that excess diesel vehicle nitrogen oxide emissions in 2015 were linked to approximately 38,000 premature deaths worldwide. It predicted this would increase to 83,600 early deaths in 2040 unless action was taken to reduce emissions.

Susan Anenberg, co-Founder of Environmental Health Analytics, LLC, said: ‘The consequences of excess diesel NOx emissions for public health are striking.

‘In Europe, the ozone mortality burden each year would be 10% lower if diesel vehicle nitrogen oxide emissions were in line with certification limits.’

The study was conducted by scientists for the International Council on Clean Transportation and Environmental Health Analytics, LLC.