Mr Brown said: "Albert Einstein is said to have observed, 'Insanity is doing the same thing over and over, and expecting different results.' Were he around to see it, Einstein might call our current renewable-fuel policy insane.

"Every year since 2009, the Environmental Protection Agency (EPA) has missed its deadline to set the required volumes of ethanol and biodiesel that must be blended into the nation’s motor-fuel supply under the schedule known as the Renewable Fuel Standard (RFS). Every year, economic chaos is the result.

"The volumes are required by statute to be set by 30 November of the preceding year. Last year, however, the volumes were set in August — eight months into the year to which the RFS applied. This year, the EPA released a proposed RFS with significant reductions to the prescribed volumes, but has since hinted they might subsequently raise those volumes when the final standard is set, sometime in June — halfway into the compliance period."