A group of four senators led by Sen. Barbara BoxerBarbara Levy BoxerHillicon Valley: Ocasio-Cortez clashes with former Dem senator over gig worker bill | Software engineer indicted over Capital One breach | Lawmakers push Amazon to remove unsafe products Ocasio-Cortez blasts former Dem senator for helping Lyft fight gig worker bill Only four Dem senators have endorsed 2020 candidates MORE (D-Calif.) are calling for the resignation of Environmental Protection Agency Administrator Stephen Johnson, saying that he gave misleading testimony to a Senate committee.

Johnson told the Senate Environment and Public Works Committee in January that he had denied a waiver to California that would have allowed it to enact its own fuel efficiency standards because the state failed to meet necessary criteria. But Boxer and three other senators said Wednesday that Johnson's testimony conflicted with that of an aide, who said that the waiver was denied partly because President Bush opposed it.

Boxer, chairwoman of the Senate Envionment and Public Works Committee, had supported the California standards, which are stricter than federal ones. She again chastised Johnson Tuesday for his decision.

"He has become a secretive and dangerous ally of polluters, and we cannot stand by and allow more damage to be done," she said in a statement. "We have lost all confidence in Stephen Johnson's ability to carry out EPA's mission in accordance with the law. I call on Administrator Johnson to immediately resign his position."

Sens. Amy KlobucharAmy Jean KlobucharDeVos calls Democratic presidential hopeful's education plans 'crazy' Senate Democrats want Warren to talk costs on 'Medicare for All' Biden struggles to reverse fall MORE (D-Minn.), Sheldon WhitehouseSheldon WhitehouseDemocrats introduce 'THUG Act' to block funding for G-7 at Trump resort The Hill's Morning Report - Tempers boil over at the White House Democrats urge Rick Perry not to roll back lightbulb efficiency rules MORE (D-R.I.), and Frank Lautenberg (D-N.J.) joined Boxer's call for Johnson to step down.

The four Democrats and Sen. Bernie SandersBernie SandersWarren says making Israel aid conditional on settlement building is 'on the table' Warren says she will unveil plan to finance 'Medicare for All' Ocasio-Cortez says endorsing Sanders early is 'the most authentic decision' she could make MORE (I-Vt.) have also asked for a federal probe into whether Johnson's testimony was false or misleading. Download their letter to Attorney General Michael Mukasey here.