A group of former Republican Environmental Protection Agency (EPA) chiefs on Tuesday denounced the Trump administration's leadership surrounding issues related to science.

William Reilly, Lee Thomas and Christine Whitman, who served as EPA heads under Republican presidents, said in an interview with ABC News that the environmental agency under Trump was "undermining" science and that its approach to climate change was potentially "catastrophic."

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The former EPA chiefs made the comments just before testifying during a House Energy and Commerce Subcommittee hearing that focused on the direction of the agency.

Whitman, who led the EPA under former President George W. Bush voiced alarm over "the disrespecting of science in the administration and the undermining of science and the importance of science," ABC News noted.

"If we continue business as usual, it's catastrophic," Reilly, who led the agency under President George H.W. Bush, added. "We're the number two emitter in the world after China."

Thomas, who served as EPA head under former President Ronald Reagan, said Reagan would have called on the agency to recommit its main objectives.

"Change the direction, change the management and go back to the mission of the agency," Thomas told ABC News. "That's what I think President Reagan would say, 'That's not how I want this agency to operate.'"

The three warned that the progress the U.S. was making in regards to clean air and water was beginning to "backslide." Asked to grade EPA leadership, the three responded with a "D" or a "littler lower."

The former administrators echoed their criticism during testimony later Tuesday.

"Today, as never before, the mission of EPA is being seriously undermined by the very people who have been entrusted with carrying that mission out,” Whitman said during her opening remarks.

The hearing occurred as the Trump administration continues to roll back environmental regulations imposed by former President Obama's administration. The moves have led to increased scrutiny over how the agency is responding to warming global temperatures.

Andrew Wheeler Andrew WheelerOVERNIGHT ENERGY: California seeks to sell only electric cars by 2035 | EPA threatens to close New York City office after Trump threats to 'anarchist' cities | House energy package sparks criticism from left and right EPA threatens to close New York City office after Trump threats to 'anarchist' cities The conservative case for phasing out hydrofluorocarbons MORE, the current head of the EPA, said in March that he believed the threat posed by climate change is “50 to 75 years out." He also said in an ABC interview in February that he did not believe that climate change had reached a "crisis" level.

Reilly took issue with the characterizations, pointing to studies that have shown severe consequences of climate change.

Trump has repeatedly questioned the impacts of climate change during his presidency. The president last week dismissed Prince Charles’s concerns about the negative effects of climate change, insisting that weather “changes both ways.”