President Trump on Tuesday said if the feds planted “spies” inside his campaign, it would be the biggest political scandal in US history — and then refused to offer support for Deputy Attorney General Rod Rosenstein.

“A lot of people are saying that they had spies in my campaign. If they had spies in my campaign, that would be a disgrace to this country. That would be one of the biggest insults that anyone has ever seen,” the president said during a White House sitdown with South Korean President Moon Jae-in.

“It would be very illegal aside from everything else. It would make probably every political event ever look like small potatoes. So we want to make sure that there weren’t. I hope there weren’t, frankly.”

Trump, in a weekend-long Twitter rant, accused the intelligence community of infiltrating his campaign, and demanded that the FBI launch a probe into special counsel Robert Mueller’s investigation of Russian meddling in the election and possible collusion with Trump’s campaign.

Rosenstein responded Monday by referring the issue to the bureau’s inspector general’s office for a review.

But, asked Tuesday if he had confidence in Rosenstein, the commander-in-chief bristled at the question.

“What’s your next question, please? Excuse me, I have the president of South Korea here. He doesn’t want to hear these questions, if you don’t mind,” he snapped.

Trump and his lawyer, Rudy Giuliani, pounced on news that broke last week that the FBI’s investigation into Russian efforts to meddle in the 2016 election included the use of government informants, including University of Cambridge professor emeritus Stefan A. Halper, an American.

Team Trump described Halper — who met with Trump’s then-aides Carter Page, George Papadopoulos and Mike Flynn — as part of a so-called deep state political operation out to undermine his election.

Halper met with the advisers after the FBI had already had evidence that they had ties to Russia, and sources have told multiple news outlets that he was not a spy but was trying to gather more information about the advisers’ Russia ties.