Michael Heaver made the claim after Democratic Speaker Nancy Pelosi said she did not want to see her party’s nominee take on the president in a public debate. But Ms Pelosi said the reason why she did not want to see former Vice President Mr Biden face-off with Mr Trump was because of her lack of confidence in the Republican leader.
She said at a press conference: “Don’t tell anybody I told you this, especially don’t tell Joe Biden.
“I don’t think that there should be any debates.”
She hit out at Mr Trump, saying he has shown no respect for “truth, evidence, data and facts”.
Ms Pelosi continued: “I wouldn’t legitimise a conversation with him, nor a debate in terms of the presidency of the United States.”
Ms Pelosi said she would instead like to see Mr Trump and Mr Biden answer questions individually.
She accused Mr Trump of “stalking” his opponent Hillary Clinton during the presidential debates in 2016.
But Mr Heaver took her speech as an indication of her lack of trust in Mr Biden.
READ MORE: Nigel Farage ‘sticks his neck out’ with bombshell US election forecast
The Brexit Party leader said those glued to the polls may be surprised by the results of the election, just as they were following the 2016 EU referendum.
In the op-ed published in Newsweek, Mr Farage added: “The fact is that in 2016, the pollsters were wrong about Brexit, and they were wrong about Trump.
“Why? One simple part of the answer to that question is that so many voters were shy of telling these opinion-gatherers their true feelings.”
Ms Pelosi’s scathing review of Mr Trump came ahead of the final night of the Republican National Convention.
The president is planning on launching a fierce attack on his rival in a speech on the White House South Lawn.
He is expected to say: “At no time before have voters faced a clearer choice between two parties, two visions, two philosophies, or two agendas.
“We have spent the last four years reversing the damage Joe Biden inflicted over the last 47 years.”
Excerpts from Trump’s speech were provided by a source on condition of anonymity.
Mr Biden is leading in opinion polls ahead of the November 3 election.