During the last weeks of his presidency, Donald Trump and his allies pressured the Justice Department to investigate unsubstantiated claims of voter fraud in the 2020 election, despite the fact his former attorney general had said there was no evidence of widespread fraud, according to emails released by the House Oversight Committee.

The emails show the extent to which Mr Trump, his White House chief of staff and other allies pressured then-acting Attorney General Jeffrey Rosen to join in the Trump campaign’s failing efforts to challenge the election result, including suggesting filing a brief with the US Supreme Court.

They reveal in new detail how Mr Trump pressured the US government to engage in challenging the 2020 election over false claims, even though officials at Homeland Security and Justice, as well as Republican election leaders across the country, repeatedly said there had been no widespread fraud.

Former Attorney General William Barr, a long-time Trump loyalist, was among those who said there was no evidence of widespread fraud.

The emails sent to Mr Rosen include debunked conspiracy theories and false information about voter fraud. Mr Trump’s claims about the election helped spur on the mob that stormed the US Capitol on January 6 in a failed effort to stop the certification of Joe Biden’s victory.

In one instance, Mr Trump’s chief of staff, Mark Meadows, tried to have Mr Rosen investigate conspiracy theories and pushed the acting attorney general to meet an ally of Trump lawyer Rudy Giuliani who was pitching unfounded election conspiracies that Italy was using satellites and military technology to change votes.

After Mr Rosen forwarded Mr Meadows’s email, Rich Donoghue, the acting deputy attorney general, sent a note to Mr Rosen that said, “pure insanity”.

Mr Rosen wrote back that he was asked to have the FBI meet Mr Giuliani’s associate and he said no, insisting the man could follow the FBI’s normal protocol for tips and just call the public tip line or take his information to an FBI field office.

But Mr Rosen said Mr Giuliani was “insulted” by the answer.

“Asked if I would reconsider, I flatly refused, said I would not be giving any special treatment to Mr Giuliani or any of his ‘witnesses,’ and re-affirmed yet again that I will not talk to Mr Giuliani about any of this,” Mr Rosen wrote.

On December 14, the day Electoral College votes were certified, Mr Trump’s White House assistant sent a note to Mr Rosen with the subject “From POTUS,” an acronym for president of the United States.

The email included talking points on alleged voter fraud in Antrim County, in a key battleground state, Michigan, such as claims like “a Cover-up is Happening regarding voting machines in Michigan”, and “Michigan cannot certify for Biden”.

Moments later Mr Trump’s assistant sent the same documents to the US attorneys in the eastern and western districts of Michigan.