Donald Trump insisted on Saturday that when he told senior justice department officials to “Just say that the election was corrupt [and] leave the rest to me”, he was not attempting to subvert US democracy, but to “uphold the integrity and honesty of elections and the sanctity of our vote”.

The former president’s restatement of his lie that his defeat by Joe Biden was the result of electoral fraud came a day after Washington was rocked by news of his December call with acting attorney general Jeffrey Rosen and Richard Donoghue, a senior DoJ official.

Trump’s pressure on federal and state officials to overturn his national defeat and state losses to Biden has been well documented. Cases mounted by his campaign claiming electoral fraud were repeatedly thrown out of court.

Republicans in states including Arizona and Wisconsin are pursuing controversial election audits and investigations. Many GOP-controlled states are pursuing laws which critics say aim to restrict ballot access among those likely to vote Democratic, or make it easier to overturn results.

But on Friday, the House oversight committee released memos taken by Richard Donoghue, a senior DoJ official, regarding a call with Rosen on 27 December. The memos brought Trump’s startling demand to light.

One Washington editor, Benjy Sarlin of NBC News, wrote on Twitter: “We can’t take a continuous historic scandal for granted just because he says it out loud all the time. These are Watergate-level allegations.”

Richard Nixon resigned in 1974 to avoid impeachment over the Watergate scandal, which concerned dirty tricks against political opponents including the committal of crimes. Trump was impeached for a second time after his lies about electoral fraud stoked the deadly assault on the US Capitol on 6 January.

Ten Republicans in the House and seven in the Senate turned against him but he retained enough support to avoid conviction on a charge of inciting an insurrection and remains able to run for federal office.

Earlier this week, all eyes in Washington were on the first hearing staged by a House select committee to investigate the Capitol assault.

Harry Dunn, a Capitol police officer, was one of four law enforcement officers who provided emotional testimony about the attack by Trump supporters.

Like the other officers he appealed for the Democrats and Liz Cheney and Adam Kinzinger, two anti-Trump Republicans on the panel, to investigate the political genesis of the assault.

“If a hitman is hired and he kills somebody,” Dunn said, “the hitman goes to jail. But not only does the hitman go to jail, the person who hired them does.

“There was an attack carried out on 6 January and a hitman sent them. I want you to get to the bottom of that.”

Trump told supporters to march on the Capitol and “fight like hell” to overturn his defeat. His conversations on the day with senior Republicans including the minority leader, Kevin McCarthy, and Jim Jordan of Ohio are the subject of fierce speculation.

Trump referred to Jordan and other Republicans during his conversation with Rosen and Donoghue, according to Donoghue’s memo. Trump was told “Much of the info you’re getting is false” and “We look at allegations but they don’t pan out”. He replied that he had allies in Congress who would pursue ways to overturn the election.

Jordan was one of almost 150 Republicans in the House and Senate who lodged objections to results in Arizona or Pennsylvania or both. Such objections made on the night of 6 January, after rioters who sought lawmakers to capture and possibly kill had been expelled from the Capitol, made no difference to Vice-President Mike Pence’s certification of Biden’s win.

Trump retains a grip on the Republican party and has continuously flirted with confirming another run for the White House in 2024. Doing so may be one way to dodge legal troubles which deepened on Friday with a DoJ order that his tax returns be released to another House committee.

In his statement on Saturday, Trump called Democrats who control the House oversight committee “corrupt and highly partisan”.

The documents released, he claimed, “were meant to uphold the integrity and honesty of elections and the sanctity of our vote … it is time for Congress and others to investigate how such corruption was allowed to take place rather than investigating those that are exposing this massive fraud on the American people”.

On Friday, Carolyn Maloney, chair of the House oversight committee, said: “These handwritten notes show that President Trump directly instructed our nation’s top law enforcement agency to take steps to overturn a free and fair election.”