Mercedes-Benz’s decision to complete upgrades to hundreds of thousands of UK-owned diesel vehicles could prompt a push to prevent the “death of diesel”, it has been claimed.

BMW and Audi have both agreed to retrofit more than 50% of its “Euro 5” diesel-engine cars with software that will reduce their emissions in an agreement brokered with the Bavarian state government as Mercedes embarks on its £195 million “service action”.

While Dailmer, which produces Mercedes-Benz vehicles, was unable to reveal the exact improvements its engine upgrades would make to emissions, Audi and BMW claimed their measures – applicable to vehicles built between 2009 and 2011 – could reduce nitrogen oxide emissions by 20% over the next five years.

BMW chief executive Harald Krüger said: “Even just talking about it unsettles millions of drivers.

“For this reason we are supporting the Bavarian State Government’s initiative to achieve overall and sustainable improvement in air quality in our cities.”

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Earlier this month French authorities announced an intention to banthe sale of any car that uses petrol or diesel fuel by 2040.

Nicolas Hulot, a veteran environmental campaigner who was appointed by new French President Emmanuel Macron, announced the planned ban as part of plan which would see France become carbon neutral by 2050.

The stamen comes two and a half years after the French Government announced its plan to "progressively ban diesel vehicles starting in 2015".

Norway and the Netherlands, meanwhile, both want to move to electric-only vehicles by 2025.

Banning combustion engines – which currently make up 95% of Europe’s transport mix – “would endanger 426,000 jobs” in Germany alone, according to the Ifo Institute, the Financial Times reported.