(Reuters) - Democratic lawmakers on Monday asked the Environmental Protection Agency’s inspector general to investigate whether two senior agency officials violated ethics rules by helping reverse an enforcement decision against their former client company.

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The request comes as Democrats, who now control Congress and oppose President Donald Trump’s push to roll back environmental regulation to help businesses, scrutinize top officials at EPA who have worked as industry lobbyists in the past.

House energy committee chairman Frank Pallone and Senators Sheldon Whitehouse and Tom Carper asked the acting inspector general of the EPA to investigate whether the agency’s Assistant Administrator Bill Wehrum and Senior Counsel David Harlow violated federal ethics law.

At issue is their alleged involvement in a December 2017 EPA memo that changed agency policy in a way that benefited DTE Energy, a client of Wehrum and Harlow at their previous employer, Hunton & Williams, a law firm representing energy industry companies.

DTE had been in a legal battle with the EPA since 2010 over whether the agency could fine it for expanding a coal-fired power plant in Michigan without having added new emissions controls, even before any significant increase in pollution from the facility had occurred.

In the memo, then-Administrator Scott Pruitt changed the EPA’s stance to agree with DTE that fines should come only after emissions increase, not before - a decision that effectively took EPA’s preventative effort to fine DTE off the table.

“The DTE memo is plainly a substantial decision that had a direct and predictable effect on a particular matter involving a client represented by their former law firm,” the lawmakers wrote.

EPA spokesman John Konkus said EPA appointees receive rigorous ethics training from career ethics officials.

“Each of them understand and strive to uphold their ethical obligations,” he said.

Wehrum told the Washington Post, which first reported on the officials’ involvement in the memo, that he believed he complied with agency ethics policies.

“I have, from day one, tried to be absolutely strict and assiduous as to what I do about complying with my ethical obligations,” Wehrum told the Washington Post.