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Environmentalists and consumer advocacy groups are castigating automakers for supporting the Trump administration’s effort to relax fuel economy standards, amid fresh warnings from a Democratic leader that the plan won’t deliver promised safety benefits and will raise costs for consumers.

Senator Tom Carper, a Democrat from Delaware, said the administration’s latest draft plan^[2] for fuel economy and greenhouse gas standards for autos, which is now being reviewed by the White House, fails to deliver many of the benefits promised when it was initially proposed in 2018. Although the Trump administration backed off from a harsher initial plan that would have frozen requirements for six years, Carper said the new approach — built on a 1.5% annual increase in the stringency of the mandates — may be even worse.

“The SAFE vehicles rule, if finalized in its present form, will lead to vehicles that are neither safer, nor more affordable or fuel efficient,” Carper said in a letter late Jan. 22 to the head of the Office of Information and Regulatory Affairs, which is now examining the proposal.

Carper’s missive comes amid a broad pressure campaign against the Trump administration vehicle plan — which has yet to be released — and the automakers that have endorsed part of it. Newspapers in Detroit, Sacramento and Washington on Jan. 23 published an advertisement containing an open letter by environmental groups calling out Toyota Motor Corp., General Motors Co., Fiat Chrysler Automobiles NV and other carmakers.

Those companies backed the Trump administration in lawsuits that challenged its decision to strip California’s authority to set tougher greenhouse gas emissions rules than federal regulators, a key element in President Donald Trump’s sweeping plan to reshape auto efficiency rules.

“We should be producing the cars of the future, not ceding the clean-car market to other countries,” Gina McCarthy, president of the Natural Resources Defense Council and an Environmental Protection Agency official during the Obama administration, said in a press release announcing the letter. “It’s unacceptable for these auto executives to side with President Trump as he works to endanger the health and welfare of millions of Americans,” she said.