Trump's directive to the White House counsel, David Warrington, in consultation with Attorney General Pam Bondi, ratchets up the pressure behind Trump's longstanding criticism of Biden's mental ability. The probe comes amid similar inquiries at the Justice Department and in a House committee.
"This conspiracy marks one of the most dangerous and concerning scandals in American history," Trump wrote in his order. "The American public was purposefully shielded from discovering who wielded the executive power, all while Biden's signature was deployed across thousands of documents to effect radical policy shifts."
But Biden has replied in a series of recent public appearances that he was in command of his faculties. He has also been critical of Trump, arguing that his successor was taking a hatchet to the Social Security Administration.
“They are wrong,” Biden said of his alleged cognitive decline on ABC's “The View.”
Trump directed the investigation to cover whether Biden's aides coordinated to shield the public from information about Biden's mental and physical health. A new book, "Original Sin," describes aides shielding Biden from Cabinet secretaries and limiting his access. Biden recently revealed his diagnosis of prostate cancer.
Trump also directed the investigation into how Biden took executive actions during his final years in office, to determine who ordered the autopen for granting clemencies or other presidential actions.
Biden pardoned his brother, James Biden, and other relatives for unspecified crimes during his final days in office. Biden had previously pardoned his son, Hunter Biden, after gun and tax convictions.
At the Justice Department, pardon attorney Ed Martin said he would investigate Biden's pardons and use of the autopen.
Congressional Republicans have long argued that the president profited from his son's and brother's overseas business deals, which the family denied. The chairman of the House Oversight and Accountability Committee, Rep. James Comer, R-Kentucky, has asked former Biden aides to sit for transcribed interviews about his mental fitness for office.
Trump notes special counsel's finding about Biden's condition
Trump's order highlights a particular sore point involving the different treatment of him and Biden in retaining classified documents after leaving office.
Justice Department special counsel Jack Smith charged Trump with unlawfully retaining more than 100 classified documents at his Florida estate, Mar-a-Lago, where they were retrieved 18 months after he left office during an FBI search. The charges were dropped when Trump was elected to a second term under a policy against prosecuting a sitting president.
Special counsel Robert Hur decided against charging Biden for classified documents found at his Delaware home and a Washington, D.C., office during a search Biden invited. Hur concluded jurors would have found Biden "a sympathetic, well-meaning, elderly man with a poor memory."
"For years, President Biden suffered from serious cognitive decline," Trump wrote. "The Department of Justice, for example, concluded that, despite clear evidence that Biden had broken the law, he should not stand trial owing to his incompetent mental state."