U.S. Sen. Sherrod Brown (D., Ohio) will oppose President Trump’s nominees for administrator of the Environmental Protection Agency and secretary of Labor, he said Monday.

Senator Brown’s decision to oppose Scott Pruitt for the EPA followed Mr. Pruitt’s hearing before the Senate Environment and Public Works Committee last week.

“The core mission of the EPA is to make sure our children have clean water to drink and clean air to breathe, and Scott Pruitt is not up to the task,” he said in a statement released by his office.

“Pruitt’s record speaks for itself: he has protected polluters over families, done the work of campaign donors instead of the public, and spent this decade trying to undermine the very agency he wants to lead,” Mr. Brown’s statement said.

He said Labor nominee Andrew Puzder “is against raising the minimum wage, against paid sick leave, and against increased overtime protections.”

“By all measures, he has fought against, not for, U.S. workers and has no place leading the department tasked with protecting them. I’ll oppose his nomination to serve as Labor Secretary because working Ohioans deserve better wages and a safe, healthy workplace,” Mr. Brown said.

In a statement in December, President Trump said Mr. Pruitt, the Oklahoma attorney general, was an expert on constitutional law with a “deep understanding of the impact of regulations on both the environment and the economy.”

Mr. Puzder, a native of Cleveland, is president and CEO of CKE Restaurants, Inc., which owns Hardee’s.

Of six cabinet votes held so far, Mr. Brown has supported four and opposed two.