One of former US EPA chief  Scott Pruitt’s most controversial decisions has been almost immediately reversed by the man he has been replaced by in the US environment agency.

Andrew Wheeler, the acting administrator of the Environmental Protection Agency, has reversed the final policy act of his predecessor, Scott Pruitt.

Mr. Wheeler’s outlined the decision in a memo  to his top policy staff, formally vacating the move Pruitt made on his last day in office before resigning amid a host of ethics issues.

Pruitt had told manufacturers that the agency would not enforce a cap on what are known as “glider” trucks — new trucks delivered without a driveline and  then fitted with older and less efficient engines by various dealers around the USA.

“I have concluded that the application of current regulations to the glider industry does not represent the kind of extremely unusual circumstances that support the EPA’s exercise of enforcement discretion,” Mr. Wheeler wrote.

Mr. Wheeler has worked during his first three weeks as the EPA’s acting chief to put distance between himself and Mr. Pruitt by addressing his staff, issuing a public schedule of his activities and taking questions from journalists. The about-face on gliders represents the first sign that Mr. Wheeler may seek to distinguish himself from Pruitt on policy as well.

“With Mr. Pruitt out, I’m glad to see the EPA will reverse one of the most egregious — and likely illegal — environmental proposals of his tenure,” said Senator Tom Carper of Delaware, the top Democrat on the Senate Environment and Public Works Committee.

He called the reversal “a step in the right direction” but he criticised a longer-term EPA plan that aims to eventually exempt glider trucks from greenhouse gas regulations.

Glider kits are new trucks that come without an engine or transmission — the name comes from the idea that they are engineless, like gliders. Older engines are then installed, and the resulting vehicles produce as much as 55 times the amount of air pollution as trucks with modern emissions controls.

They currently account for about 5 per cent of all heavy-duty trucks on US roads.

The Obama administration had estimated that, left unchecked, gliders could generate a third of the truck fleet’s soot and other pollutants that contribute to smog and acid rain and sought to limit their annual production to 300 vehicles through the end of 2019.

Those restrictions were supported by a mix of public health and environmental organizations as well as major companies like UPS, the largest truck fleet owner, and Volvo Group, one of the largest truck manufacturers. But the E.P.A. under Mr. Pruitt began the process of repealing the rule after lobbying by a small number of dealers and manufacturers that sell glider trucks.

Scott Pruitt resigned  on 5thJuly,but before he left office he notified manufacturers that the agency would not enforce the caps. An agency spokeswoman also indicated the E.P.A. might formally delay the caps until December 2019, by which point it hoped to have them permanently repealed.

The United States Court of Appeals stayed Mr. Pruitt’s loophole on 18 July . Joanne Spalding, chief climate counsel at the Sierra Club, said in a statement that Mr. Wheeler’s decision to officially reverse course on the decision amounted to having “conceded defeat.”

Mr. Wheeler in the memo indicated that regulatory process to repeal the Obama-era rule will still move forward. But, he said, the EPA will not offer any other “no action” assurance to companies. Instead the agency “shall continue to move as expeditiously as possible on a regulatory revision regarding the requirements that apply to the introduction of glider vehicles.”

Molly Block, an EPA spokeswoman, confirmed the reversal and said Mr. Wheeler made the decision after consulting with agency staff and in light of pending administrative and judicial petitions and motions.