President of the United State Donald Trump, on Wednesday directed his administration to investigate his predecessor Joe Biden’s actions as president, alleging aides masked the former president’s “cognitive decline” and casting doubts on the legitimacy of his use of the autopen to sign pardons and other documents.

However, Biden responded in a statement Wednesday night: “Let me be clear: I made the decisions during my presidency. I made the decisions about the pardons, executive orders, legislation, and proclamations. Any suggestion that I didn’t is ridiculous and false.”

The Justice Department under Democratic and Republican administrations has recognized the use of an autopen to sign legislation and issue pardons for decades, Trump presented no evidence that Biden was unaware of the actions taken in his name, and the president’s absolute pardon power is enshrined in the U.S. Constitution.

“This conspiracy marks one of the most dangerous and concerning scandals in American history,” Trump wrote in a memo. “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.”

Trump directed Attorney General Pam Bondi and White House counsel David Warrington to handle the investigation.

The U.S. president frequently suggests that Biden was wrong to use an autopen, a mechanical device that replicates a person’s authentic signature. Although they’ve been used in the White House for decades, Trump claims that Biden’s aides were usurping presidential authority.

Biden issued pardons for his two brothers and his sister shortly before leaving office, hoping to shield them from potential prosecution under Trump, who had promised retribution during last year’s campaign. Other pardon recipients included members of a congressional committee that investigated the Jan. 6, 2021, riot at the U.S. Capitol.

Trump often suggests that his political opponents should be investigated, and he has directed the Justice Department to look into people who have angered him over the years.

Meanwhile, House Oversight Chairman James Comer of Kentucky, a Republican, requested transcribed interviews with five Biden aides, alleging they had participated in a “cover-up” that amounted to “one of the greatest scandals in our nation’s history.”

“These five former senior advisors were eyewitnesses to President Biden’s condition and operations within the Biden White House,” Comer said in a statement. “They must appear before the House Oversight Committee and provide truthful answers about President Biden’s cognitive state and who was calling the shots.”

Interviews were requested with White House senior advisers Mike Donilon and Anita Dunn, former White House chief of staff Ron Klain, former deputy chief of staff Bruce Reed and Steve Ricchetti, a former counselor to the president.

Comer reiterated his call for Biden’s physician, Kevin O’Connor, and former senior White House aides Annie Tomasini, Anthony Bernal, Ashley Williams and Neera Tanden to appear before the committee. He warned subpoenas would be issued this week if they refuse to schedule voluntary interviews.

“I think that people will start coming in the next two weeks,” Comer told reporters. He added that the committee would release a report with its findings, “and we’ll release the transcribed interviews, so it’ll be very transparent.”

Democrats have dismissed the effort as a distraction.