Eighteen major car companies have written to Donald Trump urging him to overturn a fuel efficiency target set by the Obama administration.

Under the regulation, cars would have to run for 54.5 miles per gallon or better by 2025, saving American motorists $1.7 trillion (£1.4 trillion) in fuel costs over the lifetime of their vehicles — but costing the car industry $200bn over 13 years.

However the election of Mr Trump – who has downplayed the need to cut fossil fuel emissions – clearly represents an opportunity for the motor industry.

The letter was written by the chief executives of General Motors, Ford, Fiat Chrysler and the leading US executives of Volkswagen, Toyota, Honda, Nissan and Hyundai among others.

The letter praised Mr Trump’s “personal focus on steps to strengthen the economy in the United States and your commitment to jobs in our sector”.

And it also claimed the fuel efficiency target could “threaten future production levels, putting hundreds of thousands and perhaps as many as a million jobs at risk”.

The chief executives asked Mr Trump to reopen a review of the target “without prejudging the outcome”.

The worst countries in the world for air pollution deaths Show all 10 1 /10 The worst countries in the world for air pollution deaths The worst countries in the world for air pollution deaths Ukraine A radioactive sign hangs on barbed wire outside a café in Pripyat. The worst countries in the world for air pollution deaths Bulgaria Mandatory Credit: Photo by NUKARI/REX (407890f) A power plant outside Sofia STOCK OF BULGARIA - FEB 2003 Rex Features The worst countries in the world for air pollution deaths Belarus The worst countries in the world for air pollution deaths Russia The worst countries in the world for air pollution deaths Armenia The worst countries in the world for air pollution deaths Bosnia and Herzegovina Women wearing masks walk in front of academy of fine arts as smog blankets Sarajevo, Bosnia and Herzegovina December 23, 2015. With severe air pollution affecting the city nestled among the mountains, the authorities have declared the first level of preparedness, advising the segment of the population that is at health risk to reduce movement in the mornings and evenings, appealing to drivers to use motor vehicles less and ordering heating utilities to lower the emission of harmful gases. REUTERS/Dado Ruvic REUTERS The worst countries in the world for air pollution deaths Georgia The worst countries in the world for air pollution deaths Hungary TOXIC SPILL, AJKA, HUNGARY-OCTOBER 9, 2010: This is an image of the toxic spill in Ajka, Hungary affecting the villages of Kolontar and Devecsar Hungary. (credit: DigitalGlobe) DigitalGlobe The worst countries in the world for air pollution deaths China The worst countries in the world for air pollution deaths Moldova

Gloria Bergquist, a spokeswoman for the Alliance of Automobile Manufacturers, said that the carmakers were “seeking a restoration of the process, that's all. This is a reset.”