Donald Trump is further escalating his online feud with Bruce Springsteen and other major recording acts, posting a rant on Truth Social early Monday morning calling for a “major investigation” into Springsteen, Beyoncé and Bono’s support for Kamala Harris during her presidential campaign.

“HOW MUCH DID KAMALA HARRIS PAY BRUCE SPRINGSTEEN FOR HIS POOR PERFORMANCE DURING HER CAMPAIGN FOR PRESIDENT,” Trump wrote in all caps. “WHY DID HE ACCEPT THAT MONEY IF HE IS SUCH A FAN OF HERS? ISN’T THAT A MAJOR AND ILLEGAL CAMPAIGN CONTRIBUTION? WHAT ABOUT BEYONCÉ?”

Trump suggested that Harris had paid for the stars’ endorsements “under the guise of paying for entertainment.” And fitting to the president’s fixation on crowd sizes at political events, Trump said the appearances were “a very expensive and desperate effort to artificially build up her sparse crowds.”

“For these unpatriotic ‘entertainers,’ this was just a CORRUPT & UNLAWFUL way to capitalize on a broken system,” Trump wrote.

In a follow up post, Trump claimed the Harris campaign paid Beyoncé $11 million “to walk onto a stage, quickly ENDORSE KAMALA, and walk off to loud booing for never having performed, NOT EVEN ONE SONG!” Beyoncé’s mother Tina Knowles denied similar claims that her daughter was paid $10 million for her appearance back in November, writing on Instagram she “did not receive a penny.”

“They are not only lying and disrespecting Beyoncé’s name but they are trying to further discredit the power of our vice president,” Knowles wrote at the time. Other stars who endorsed Harris and appeared at rallies such as Oprah Winfrey have also denied getting paid.

Trump’s latest missives come days after the president vaguely threatened Springsteen after the rock star admonished the Trump administration during a concert in the U.K. on Wednesday, telling the crowd that the U.S. is “currently in the hands of a corrupt, incompetent, and treasonous administration.”

In response, Trump called Springsteen “adried out ‘prune’ of a rocker” and said he “ought to KEEP HIS MOUTH SHUT until he gets back into the Country, that’s just ‘standard fare’. Then we’ll all see how it goes for him!”

Springsteen, for his part, hasn’t let up, doubling down on his claims about Trump during another U.K. show at Co-Op Live this weekend.

“In my home, they’re persecuting people for their right to free speech and voicing their dissent. That’s happening now,” Springsteen said Saturday in a video captured by the Los Angeles Times. “In America, the richest men are taking satisfaction in abandoning the world’s poorest children to sickness and death. That’s happening now. In my country, they’re taking sadistic pleasure in the pain they inflict on loyal American workers.”