Lawyers for Donald Trump have asked a judge to dismiss a federal election subversion case against him, arguing the Republican is immune from prosecution for actions they say were taken in his official role as president.

The motion amounts to the most pointed attack yet by defence lawyers on the federal case in Washington DC charging Trump with plotting to overturn the results of the 2020 presidential election he lost to Democrat Joe Biden.

It tees up a fight over the scope of presidential power, forcing courts to wrestle with whether the actions Trump took in his failed bid to remain in office fell within his duties as commander in chief or whether they strayed far outside his White House responsibilities and were there therefore illegal.

“Breaking 234 years of precedent, the incumbent administration has charged President Trump for acts that lie not just within the ‘outer perimeter’, but at the heart of his official responsibilities as president,” the defence motion says.

“In doing so, the prosecution does not, and cannot, argue that President Trump’s efforts to ensure election integrity, and to advocate for the same, were outside the scope of his duties.”

The presidential immunity argument had been foreshadowed for weeks by defence lawyers as one of multiple challenges they intend to bring against the indictment. A judge had set a deadline for Monday for pre-trial motions like the one to dismiss the case.

Prosecutors appeared to anticipate the immunity argument, writing in the indictment that although political candidates are permitted to challenge election losses and to even falsely claim victory, Trump’s actions strayed far beyond what is legally permissible in the run-up to the January 6 2021, riot at the US Capitol, when pro-Trump rioters stormed the building to disrupt the counting of electoral votes.

Prosecutors are expected to contest the motion. It is not clear when US District Judge Tanya Chutkan might rule, but arguments over the motion — including an appeal if she denies the request — could delay the case.

Capitol Riot Photographer Attacked
Donald Trump supporters stormed the Capitol on January 6 2021 (John Minchillo/AP)

In their motion, defence lawyers argue that the actions that form the basis of the indictment, including urging the Justice Department to investigate claims of voter fraud and pressing state officials on the administration of elections, cut to the core of Trump’s responsibilities as commander in chief.

“Every action of the defendant charged in the indictment occurred while he was still in office as president of the United States, and, according to the prosecution, all concerned a federal government function,” they wrote.

“Given the all-consuming nature of the presidency, these facts alone strongly support the notion that the indictment is based solely on President Trump’s official acts.”

Trump’s tweets and public statements about fraud in the election and vice president Mike Pence’s role in the certification were directly related to his assertion that the election’s outcome was tainted by fraud and that the Justice Department and certain states had failed to adequately investigate it, Trump’s lawyers wrote.

Prosecutors have alleged that Trump knew the claims he was pushing about election fraud were false but did so anyway in an effort to undermine the integrity of the democratic process, but Trump’s lawyers say “the president’s motivations are not for the prosecution or this court to decide”.

The case is set for trial on March 4.