France and Spain have emerged as two of the loudest voices in upholding a ban by 2035 in the European Union on diesel and petrol cars, an issue that threatens to inflame differences between member states.

The EU's executive body, the European Commission, has said the existing target date will be reviewed by the end of this year, but the two countries are insisting on "staying on track", saying zero-emissions vehicles are "indispensable" if the bloc wants to stick to its target of reaching carbon neutrality by 2050.

Countries including Slovakia, Italy, and Germany, which have economically significant automotive sectors, have opposed the ban.

In August, Ola Kallenius, chairman of the management board of Mercedes-Benz, told German newspaper Handelsblatt "we need to do a reality check.

Otherwise, we'll drive full speed into the wall … of course we have to decarbonize but we must not lose sight of our economy".

Italy's Prime Minister Georgia Meloni is a long-standing opponent of what she has dubbed "madness ideology", and her counterpart in Slovakia, Robert Fico, says what he calls "green utopias" threaten car manufacturing in his country.

But in a letter seen by the Euronews website, France and Spain noted that much money has already been invested in making sure binding goals are achievable, and said more European cooperation was needed in the face of "unfair international competition".

"This founding choice, which has guided several tens of billions of euros of industrial investment in Europe since 2023, must not be called into question," the letter said. It went on to acknowledge the difficulties faced by the continent's auto manufacturing sector, and said the commission's imminent review of the law should be used as an opportunity to strengthen electric vehicle, or EV, production capability across Europe.

The EV sector in Europe is of particular interest to Chinese manufacturers, who have targeted it in recent years with considerable success, including the BYD brand outselling the previous market leader Tesla.

The Financial Times reported that in April, data from automotive data intelligence company Jato Dynamics showed registration of Chinese brand EVs in Europe had risen 59 percent year-on-year, and that plug-in hybrids had witnessed an eight-fold increase in demand.