He has previously said he plans to appoint a special prosecutor to investigate Mr Biden and his family members.

His son told Tucker Carlson, a conservative journalist, yesterday that Mr Trump would “fix” the justice system. “I wanted to believe that everything I grew up believing was accurate,” he said. “And it’s all bull—-. It’s just all bull—-. So we have to fix that. That’s why we fight now, to actually make it so.”

He said his father’s crimes were “at best, misdemeanour-type stuff” in a case that had “never been done before”.

“They want to put my father in jail for, you know, upwards of 100 years, depending on how you look at it,” he said, adding that “the system’s probably been broken for much longer than any of us would care to admit”.

The businessman, 46, said that unnamed “swamp” figures in Washington would try harder to prevent a second Trump presidency because he has more experience of government than during his first campaign in 2016.

“I think the notion of Trump coming back now actually scares them so much more because he has that knowledge, he has that understanding,” he said. “And I think that will make him so much more effective in a second term.”

Some Republicans have suggested that Mr Trump should follow through on his plan to bring prosecutions against “the entire Biden crime family”, either by appointing a special counsel in the federal Department of Justice or encouraging individual state attorneys to begin legal action.

Mike Collins, a Republican congressman, tweeted on Thursday night that it was “time for red state AGs and DAs [attorney generals and district attorneys] to get busy”, and suggested that Hillary Clinton could also be a target.

‘Best revenge is success’

Tim Scott, a Republican senator who has been touted as a possible running mate for Trump in November, suggested he did not agree with more political prosecutions. In a CNN interview, he said that the former president had privately told him “the best revenge is success” in the election, hinting that he would not continue the so-called “lawfare” if he won a second term.

Mike Davis, a conservative lawyer tipped for a role as US attorney general under a second Trump administration, told the news website Axios that legal proceedings should be launched against Democrats who indicted Trump in the Florida and Georgia cases.

Several House Republicans posted images of upside-down American flags – a symbol used by Trump supporters at the Capitol riots in 2021 – while Marco Rubio, a Florida senator, said the cases were “show trials” pushed by “Marxists and the far Left”.

Mike Pence, Mr Trump’s former vice-president, said the Manhattan district attorney had brought “politically motivated charges”, and that the jury’s verdict was an “outrage”.

However, Larry Hogan, a Republican Senate candidate, said the public should “respect the verdict” and “the rule of law” in the face of Mr Trump’s rebuttal.

‘Liberal hit job’

Most European politicians chose more cautious language on the trial, although Boris Johnson on Friday called it a liberal “hit job” that had “made his victory more likely”.

Rishi Sunak and Sir Keir Starmer have both declined to comment on the details of the case, but the Labour leader said he would be willing to work with whichever candidate wins the presidential election later this year.

In Russia, a Kremlin spokesman said the prosecutions were “attempts by the current authorities to eliminate political rivals by any means”.