• The United Auto Workers has filed a labor complaint against Sen. Tim Scott of South Carolina for saying striking workers should be fired.
• The complaint filed with the National Labor Relations Board accuses Scott of violating workers' rights to engage in union activity under federal law.
• Scott is running for the 2024 Republican presidential nomination.

The United Auto Workers union has filed a labor complaint against Sen. Tim Scott for saying workers should be fired for going on strike.

The complaint filed with the National Labor Relations Board on Thursday accuses the South Carolina Republican's presidential campaign of interfering with workers' rights to engage in union activity under federal law. The right to strike is protected under Section 7 of the National Labor Relations Act.

"Tim Scott threatened employees with adverse consequences if they engage in protected, concerted activity by publicly responding to a question about striking workers as follows: 'You strike, you're fired,'" UAW President Shawn Fain said in the complaint. CNBC has not independently obtained the document, but Fain confirmed its authenticity to NBC News.

When asked Monday how he would deal with labor talks, Scott told voters at an event in Fort Dodge, Iowa, that he would emulate former President Ronald Reagan, who fired thousands of striking air traffic controllers in 1981.

"Ronald Reagan gave us a great example when federal employees decided they were going to strike," the South Carolina senator said.

"He said, 'You strike, you're fired.' Simple concept to me. To the extent that we can use that once again, absolutely," Scott said.

The senator doubled down on his attack against the UAW in a statement to CNBC on Friday. Scott said the union was trying to intimidate him.

"The UAW is one of the most corrupt and scandal-plagued unions in America," Scott said. "They are showing their true colors once again and autoworkers and taxpayers will be left holding the bag together. They want to threaten me and shut me up."

When asked Wednesday to elaborate on his comments about firing striking workers, the senator said he opposed the UAW's demand for a 32-hour work week at 40 hours of pay.

"The truth is that we all pay the higher price, but the ultimate payer has been recently the American taxpayers," Scott said during an event in Windham, New Hampshire. "And so that's what I said but they only clipped it for their benefit."

CNBC has reached out to the UAW for comment. The Intercept first reported that the union had filed the complaint.

Nearly 13,000 UAW members are on strike for the seventh day at key plants in Michigan, Missouri and Ohio. Fain said the union will expand the strike Friday to 38 General Motors and Stellantis locations but leave out additional Ford facilities.

Scott's home state of South Carolina has a strong anti-union reputation. The Palmetto State is a hub for foreign car manufacturers who are taking advantage of the South's lower labor costs compared to heavily unionized Midwestern states, the traditional heart of American auto manufacturing.

Nikki Haley, who is also running for the Republican presidential nomination, proclaimed she was a "union buster" while governor of South Carolina. Haley pointed to her record of recruiting foreign car manufacturers such as Mercedes Benz and Volvo to the Palmetto State.

"I didn't want to bring in companies that were unionized simply because I didn't want to have that change the environment in our state," Haley said during an interview with Fox News.

The anti-union comments made by Scott and Haley come ahead of the second Republican presidential debate next week. Former President Donald Trump, the Republican front-runner, is skipping the debate to talk to union members in Detroit.

Trump is courting a UAW endorsement while at the same time bashing the union's leadership. The former president has said that President Joe Biden's push to transition to electric vehicles threatens the jobs of autoworkers in the U.S.

"The autoworkers are being sold down the river by their leadership, and their leadership should endorse Trump," the former president told NBC News in an interview that aired Sunday.