Senior Secret Service agents are reportedly prepared to testify that Donald Trump did not lunge for the wheel of his vehicle or physically attack the chief of his security detail after his speech near the White House on January 6 – as a former aide said he did in sworn testimony on Tuesday.

The row comes after the explosive testimony painted an unhinged and violent portrait of Trump on the day of the Capitol attack, in a shocking hearing many have seen as potentially loosening the former president’s grip on the Republican party.

CNN and other outlets reported the pushback on the alleged Secret Service incident from Tony Ornato, who was also a deputy chief of staff in the Trump White House, and Robert Engel, who was Trump’s security chief.

Cassidy Hutchinson, a former aide to Trump and his final chief of staff, Mark Meadows, appeared before the House January 6 committee for its sixth public hearing.

Her extraordinary testimony spanned nearly two hours.

In particularly striking passages, she described what she said Ornato told her was Trump’s reaction to being told that after speaking to supporters at the Ellipse – and telling a crowd he knew in part to be armed to “fight like hell” to overturn his election defeat – he could not go with the crowd to the US Capitol as planned.

Hutchinson, 25, testified that Ornato told her Trump had a “very strong, very angry response”.

Trump allegedly told Engel: “I’m the fucking president. Take me up to the Capitol now.”

When he was turned down, Hutchinson said, Trump tried to seize the steering wheel. Engel grabbed his arm and said: “Sir, you need to take your hand off the steering wheel. We’re going back to the West Wing. We’re not going to the Capitol.”

Hutchinson said “Trump then used his free hand to lunge towards Bobby Engel and when Mr Ornato recounted the story to me he motioned towards his clavicles”.

Questioned by Liz Cheney, the committee vice-chair, Hutchinson said Engel did not dispute the account when Ornato relayed it.

In the aftermath of the explosive hearing, Hutchinson was depicted as a former Trump loyalist whose testimony could prove hugely damaging, in the vein of John Dean, the White House counsel who turned on Richard Nixon during the Watergate hearings half a century ago.

Nixon resigned the presidency under threat of impeachment. Trump was impeached for a second time over the insurrection but acquitted when only seven Republican senators voted for his guilt. He remains free to run for the White House again in 2024.

On Tuesday, reporters swiftly relayed news that the Secret Service agents disputed Hutchinson’s account of events in the presidential vehicle.

Carol Leonnig of the Washington Post, author of two books on the Trump administration and a history of the Secret Service, Zero Fail, said: “Sources tell me agents dispute that Donald Trump assaulted any agent or tried to grab the steering wheel on Jan 6. They agree Trump was furious about not being able to go to Capitol with his supporters. They offer to testify under oath.”

Secret Service agents have testified before, during the impeachment of Bill Clinton.

Trump attacked Hutchinson during the hearing, using his Truth Social platform to call her a “phony”, a “leaker” and a “whacko”. He denied grabbing the steering wheel or attacking an agent.

Republicans on the House judiciary committee tweeted that Hutchinson’s evidence was “all hearsay” and added: “What a joke.”

But Steve Vladeck, a law professor at the University of Texas in Austin, said: “Don’t be distracted by claims of ‘hearsay’. That goes to whether evidence can be admitted in court, not Congress.

“The key is that Hutchinson testified under oath. If she was lying, she faces felony charges. The same can’t be said for those trying to discredit her testimony.”

Most observers thought the case for Trump facing felony charges increased after Tuesday’s hearing.

Laurence Tribe, a Harvard law professor, said the new evidence against Trump was “devastating for inciting, aiding and abetting violent insurrection”.

Tribe also said: “Whatever anybody says about [Department of Justice] reluctance to indict Trump – reluctance I abhor – failing to indict Mark Meadows along with Jeffrey Clark, John Eastman, Rudy Giuliani and Sidney Powell would be a travesty.”

Hutchinson described Meadows’ behavior on and around January 6. The chief of staff, she said, was unwilling to confront Trump but eager to be included in meetings involving Giuliani, Eastman and other Trump allies plotting to overturn the election.

Meadows and Giuliani, Hutchinson said, asked about being given presidential pardons before Trump left office.

Vladeck also said: “Holy shit, that hearing.”