Dan Scavino, who was then serving as Mr Trump's chief of staff and director of social media , allegedly claimed at a White House Christmas party that the President would "just stay in power" regardless of election rules.
The accusation was made by former Trump campaign lawyer Jenna Ellis as part of a plea bargain with Georgia state prosecutors, who have charged Mr Trump and 18 others with plotting to illegally overturn the result of the 2020 presidential election.
Footage obtained by ABC News from a confidential meeting with investigators shows Ellis describing an alarming conversation she had with Mr Scavino on or around 19 December, 2020.
"I emphasised to him [that] I thought the ability to challenge the election results was essentially over," Ellis told prosecutors during the meeting, referring to a raft of failed legal challenges launched by the Trump campaign the previous month.
"He said to me, in a kind of excited tone: 'Well, we don't care and we're not gonna leave.'"
"I said, 'what do you mean?' And he said: 'Well, the boss' – meaning President Trump, and everyone understood that's what we all called him – he said, 'the boss is not going to leave under any circumstances. We are just going to stay in power.'"
Ellis expressed doubt, telling Mr Scavino that "it doesn't quite work that way, you realise". Mr Scavino allegedly responded: "We don't care."
In response, Mr Trump's lawyer Steve Saddow told ABC that the "purported private conversation" described by Ellis was "absolutely meaningless" because Mr Trump ultimately left the White House on schedule in January 2021.
"If this is the type of bogus, ridiculous 'evidence' [Georgia] District Attorney Willis intends to rely upon, it is one more reason that this political, travesty of a case must be dismissed."
Ellis pled guilty last month to one count of aiding and abetting false statements, admitting that she had spoken with reckless disregard for the truth when she claimed without evidence that thousands of felons and under-18s had voted illegally.
In exchange for her full cooperation with prosecutors, she will avoid a prison sentence, instead paying a $5,000 fine and performing 100 hours of community service.
Before working for Mr Trump, Ellis was a prominent conservative lawyer best known for arguing that the US constitution was founded upon and must be interpreted according to Christian morality.
The Independent has asked both Ellis and Mr Scavino for comment.