Donald Trump signed legal documents challenging the results of the 2020 election that included voter fraud claims he knew to be false, a federal judge has said.

US District Court Judge David Carter issued an 18-page opinion ordering that four emails between Mr Trump and lawyer John Eastman be given to the House of Representatives committee investigating the January 6 attack on the Capitol.

He said the emails cannot be withheld because they include evidence of potential crimes.

The judge’s conclusion has no practical bearing on a separate Justice Department investigation into efforts to overturn the election, but any evidence that Mr Trump signed documents he knew to be false could at minimum be a notable data point for criminal prosecutors trying to sort out culpability for far-ranging efforts to undo the results.

The judge specifically cited claims from Mr Trump’s lawyers that Fulton County in Georgia had improperly counted more than 10,000 votes of dead people, felons and unregistered voters. Those false allegations were part of a filing his legal team made in Georgia state court on December 4 last year.

Capitol Riot Investigation
John Eastman (Susan Walsh/AP)

Later that month, Mr Eastman warned in a message that the former president had been made aware that “some of the allegations (and evidence proffered by the experts)” in the Georgia filing “has been inaccurate”.

Even after the message from Mr Eastman, the ex-president and his team filed another legal complaint that had “the same inaccurate numbers”, the judge wrote.

Mr Trump under oath verified the complaint was true to the best of his knowledge.

“The emails show that President Trump knew that the specific numbers of voter fraud were wrong but continued to tout those numbers, both in court and to the public,” Judge Carter wrote. He said the emails are “sufficiently related to and in furtherance of a conspiracy to defraud the United States”.

The ruling is the latest development in a months-long legal battle between Mr Eastman — a conservative lawyer and lead architect of Mr Trump’s last-ditch efforts to stay in office — and congressional investigators.

Mr Eastman has been trying to withhold documents from the committee on the basis of attorney-client privilege claims.

The committee has argued there is a legal exception allowing the disclosure of communications regarding ongoing or future crimes, and Judge Carter has mostly agreed, ordering the release of hundreds of emails to the House committee since the spring.

In a stunning ruling in March, the judge asserted it was “more likely than not” that Mr Trump committed crimes in his attempt to stop the certification of the 2020 election.

Judge Carter in his ruling on Wednesday said the messages he had reviewed from Mr Eastman and other lawyers show that the “primary goal” for some of the litigation was delaying or disrupting the certification of President Joe Biden’s election win.

The totality of the evidence makes clear that “Trump filed certain lawsuits not to obtain legal relief, but to disrupt or delay the January 6 congressional proceedings through the courts”, the judge wrote.

The emails from Mr Eastman are part of the House committee’s investigation into a multi-part plan by Mr Trump and his allies to overturn the 2020 election and the ensuing violence at the Capitol.

The judge ordered Mr Eastman to give the documents to the committee by the afternoon of October 28.