U.S. Sen. Michael Bennet is among the lead sponsors of a resolution introduced Wednesday calling on Environmental Protection Agency Administrator Scott Pruitt to resign, the same day White House budget officials opened an investigation into the decision to install a $43,000 soundproof phone booth in Pruitt’s office.

The measure, signed by 170 Democratic lawmakers, slams Pruitt for “repeated ethics violations, misuse of taxpayer dollars, and actions that fundamentally undermine the mission of the EPA – favoring big polluters at the expense of science, the environment, and the health of children and families.”

Pruitt has faced increasing scrutiny since reports surfaced last month that he rented a condo from the wife of a prominent energy-industry lobbyist for $50 a night – a deal Pruitt has defended as ethical. Critics have also assailed Pruitt’s spending on a 20-member security detail an internal review determined cost $3 million.

Bennet said in a statement that Pruitt’s record directing EPA policy was as alarming as his lavish spending on the taxpayer’s dime.

“Believing in climate change should be a requirement for an EPA Administrator,” Bennet said. “Not only does Administrator Pruitt fail on this front, but he’s also proven that he cannot be trusted with taxpayer dollars. I hear from Coloradans daily who are worried about the quality of our air and water as Administrator Pruitt continues stand up for polluters. Coloradans, and all Americans, deserve more from a leader. It’s time for Administrator Pruitt to resign.”

Colorado’s three Democratic House members – U.S. Reps. Diana DeGette, Jared Polis and Ed Perlmutter – signed onto the resolution. It boasts the highest number of Senate co-sponsors ever to formally calling for the removal of a cabinet member, according to a release.

Although several Republican lawmakers have issued calls for Pruitt to resign or be fired, none signed on to the resolution introduced Wednesday, indicating its chances of advancing in the GOP-controlled House and Senate are slim.

Earlier this month, President Donald Trump said in a tweet that Pruitt “is doing a great job but is TOTALLY under siege.”