U.S. billionaire Elon Musk renewed his criticism of President Donald Trump's "big, beautiful bill" on Monday, threatening that the lawmakers who support it risk losing their primaries next year.

"Every member of Congress who campaigned on reducing government spending and then immediately voted for the biggest debt increase in history should hang their head in shame!" he wrote on his social platform X.

"And they will lose their primary next year if it is the last thing I do on this Earth," he noted.

In a separate post, Musk said he will support Republican Congressman Thomas Massie of Kentucky, whom Trump criticized for voting against the bill in the House.

Trump vowed to campaign against Massie "really hard" in the GOP primary, promising "a wonderful American Patriot" would run against him.

Musk has been attacking the bill on and off since stepping down from the Department of Government Efficiency in May.

He warned that the legislation will hike the debt ceiling by 5 trillion U.S. dollars, "destroy millions of jobs in America and cause immense strategic harm to our country."

The bill could also directly affect Musk's electric carmaker, Tesla, by eliminating electric vehicle tax credits -- up to 4,000 dollars for a used EV and 7,500 dollars for a new one.

JPMorgan Chase estimates the move could cost Tesla 1.2 billion dollars.

Musk broke his brief silence over the controversial spending bill on Saturday, calling it "utterly insane and destructive" as the package is working its way through the Senate.

In response, Trump on Tuesday wrote on his social platform Truth Social that Musk knew he was "strongly against the EV Mandate" long before endorsing him for president.

"It is ridiculous, and was always a major part of my campaign," he said. "Electric cars are fine, but not everyone should be forced to own one."

"Elon may get more subsidy than any human being in history, by far, and without subsidies, Elon would probably have to close up shop and head back home to South Africa. No more Rocket launches, Satellites, or Electric Car Production, and our Country would save a FORTUNE. Perhaps we should have DOGE take a good, hard, look at this? BIG MONEY TO BE SAVED!!!" he added.