WASHINGTON -- Fines for illegal pollution have plummeted under President Trump, according to analysis by an environmental advocacy group.

The Environmental Integrity Project looked at that civil penalties paid by polluters during the first six months under Mr. Trump. The group published an analysis Thursday that found penalties were less than half their levels under each of the past three presidents.

The analysis found that Mr. Trump's Justice Department settled 26 civil cases against companies over environmental violations, totaling $12 million in penalties. That's a 60 percent drop on average from comparable time periods under presidents Barack Obama, George W. Bush or Bill Clinton, even before adjustments for inflation.

Besides reaching fewer settlements, the group said, environmental offenders also were required to perform less cleanup under Mr. Trump and make smaller reductions to future pollution.

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A spokesman for the Justice Department said Thursday it continues to "vigorously enforce" environmental laws.

The report's authors cautioned that six months represent only an eighth of a presidential term but said the early news is neither encouraging nor surprising. Mr. Trump and his Environmental Enforcement Agency chief, Scott Pruitt, have complained that federal regulations are often too onerous and stifle the growth of American businesses.

"President Trump campaigned on a promise of 'law and order,' but apparently law enforcement for big polluters is not what he had in mind," Eric Schaeffer, executive director of the Environmental Integrity Project, said in a statement. He previously served as director of EPA's civil enforcement office under both Clinton and Bush.

"If this drop-off in environmental enforcement continues, it will leave more people breathing more air pollution or swimming in waterways with more waste," Schaeffer said.

Under the first six months under Obama, the Justice Department brought 34 civil cases for violations of the Clean Air Act, the Clean Water Act and other federal environmental laws, with polluters agreeing to pay $36 million in penalties. Bush logged 31 cases with $30 million in penalties, while Clinton accounted for 45 cases with $25 million in penalties.

The group did not include settlements for pollution cleanups agreed to as part of the federal Superfund program, cases that can often drag on for decades.

The comparison between presidential administrations is more stark when figures are adjusted for inflation. For example, the $25 million in civil penalties under Clinton in the first half of 1992 would equal more than $43.5 million in today's dollars.

The Justice Department did not dispute the study's numbers, but a spokesman said figures for civil penalties do not tell the full story because they do not include fines from criminal prosecutions.

"The department continues to vigorously enforce environmental laws to better protect the American people," said Mark Abueg, a public affairs specialist at Justice. "For example, in just the last six months, (we) filed major new Clean Air Act litigation and obtained a $40 million criminal penalty in a vessel pollution case that safeguards the environment."

The $40 million fine Abueg cited was finalized in April as part of the sentencing of Princess Cruise Lines over the illegal dumping and concealment of oil-contaminated waste from its ships. However, the settlement, the largest ever in such a case, was actually negotiated under the Obama administration and announced in December -- the month before Mr. Trump took office -- as part of the company's guilty plea to felony crimes in federal court.