In his latest threat against his political enemies, President Trump is calling for President Biden to be jailed after a group of Republican senators disclosed that the FBI had obtained their phone records during the course of an investigation. Mr. Trump says he enjoys watching Mr. Biden “squirm.”

Last month, Senator Chuck Grassley, the chairman of the Judiciary Committee, disclosed in September that nearly 100 individuals aligned with Mr. Trump fell under the microscope of the FBI’s investigation into the attempt to overturn the 2020 election results. That group included a number of Republican senators whom the president either contacted or tried to contact about his desire to see Congress send the presidential election back to state legislatures, where he could have secured a second consecutive term. 

On Thursday, Mr. Trump laid blame for the FBI investigation with Mr. Biden, who has long denied any knowledge of or involvement with law enforcement’s probes into his fellow president. 

“He is a CRIMINAL AND SHOULD BE IN JAIL. A MAJOR LOWLIFE AND FAILURE,” Mr. Trump wrote in a Truth Social post, which included a link to an article from the right-leaning news website Just the News. Mr. Trump went on to call Mr. Biden, “An ugly person, both inside and out!”

“I beat him badly, and love watching him squirm now,” the sitting president wrote of his predecessor. 

The article from Just the News claims that the evidence for launching the FBI’s investigation, known as Arctic Frost, was thin. Special Counsel Jack Smith — who in two separate cases was trying to convict Mr. Trump — later took over the Arctic Frost probe as part of his broader investigation. 

Mr. Biden’s personal office did not immediately respond to an email seeking comment. 

Mr. Biden has largely been staying out of the spotlight since leaving the White House in January. Earlier this year, he announced he was battling an aggressive form of prostate cancer, though he has completed a round of radiation to treat it. Shortly after, he made public remarks at the Edward M. Kennedy Institute for the United States Senate in Massachusetts. 

The ex-president is just the latest target of Mr. Trump, who has been demanding that Attorney General Pam Bondi launch a host of investigations against political enemies. The Justice Department is already bringing charges against three chief tormentors of Mr. Trump — former FBI director James Comey, New York attorney general Letitia James, and Mr. Trump’s former national security advisor, John Bolton.

Mr. Trump has also called on Ms. Bondi to prosecute Senator Adam Schiff. He led the effort to impeach Mr. Trump for his attempt to get information from President Zelensky about Hunter Biden’s business dealings in Ukraine. The president has similarly publicly demanded that Governor JB Pritzker of Illinois and Chicago Mayor Brandon Johnson be prosecuted for fighting his attempts to deploy federal law enforcement and the military to the city.