Nigel Farage has said he could not quote Donald Trump's feelings on the BBC before the watershed following a phone call with him.
The Reform UK leader revealed he had a phone call with the US president on Friday in which Mr Trump said "is this how you treat your best ally?"
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BBC director general Tim Davie and the chief executive of BBC News, Deborah Turness, announced they had resigned on Sunday evening after questions about bias after a BBC Panorama special spliced Mr Trump's 6 January 2021 speech so it looked like he had encouraged supporters to storm Capitol Hill.
Mr Farage told Sky News people should "put yourself in Trump's shoes" as he questioned how they would feel if they were the person making sure the UK had security guarantees, and you had been "stitched up on the eve of a national election"
"What the BBC did was election interference," Mr Farage said
"If you put yourself into Trump's shoes, he made his feelings to me in no uncertain terms - in no unquotable terms."
He later said he was not sure he could reveal what words Mr Trump used "before the watershed", adding that he was "very, very unhappy".
The Reform leader said the BBC has been "institutionally biased for decades", just moments after Ms Turness arrived at the BBC's central London headquarters and admitted "mistakes are made" but said there is "no institutional bias".
Lib Dem leader Sir Ed Davey has urged Mr Farage, Kemi Badenoch and Sir Keir Starmer to condemn Mr Trump's attack on the BBC, calling it a "serious threat to our national interest".
In an open letter to the three leaders, he said: "It should not be up to foreign powers to dictate where the British people get their news from.
"We must stand united to defend our democracy from foreign interference like this - even when it comes from a crucial ally."
Earlier, the chair of the culture, media and sport committee, Dame Caroline Dinenage, told Mornings with Ridge and Frost it is "really regrettable" Mr Davie had to step down but she thought "he was right to do so".
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Dame Caroline said the BBC was "very slow to react" to a leaked report by Michael Prescott, an independent adviser to the BBC's editorial guidelines and standards board.
The dossier, sent to the BBC board and leaked to The Daily Telegraph, accused the Panorama special on Donald Trump, released a week before the 2024 US election, of being "neither balanced nor impartial - it seemed to be taking a distinctly anti-Trump stance".
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Mr Prescott also raised bias concerns about the BBC's coverage of trans issues and the war in Gaza.
Dame Caroline accused the BBC of failing to take his report seriously "until it was too late".
She said the situation "has to influence the BBC charter decisions".
The BBC's Royal Charter outlines the corporation's mission, public purposes and governance, along with specific obligations and how it is funded.
It is up for renewal in 2027, with the government currently carrying out a review to determine the BBC's future, including its funding model and mission.
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Dame Caroline said the last review, 10 years before, put integrity as the BBC's top missions.
She added: "I think the charter has to look at how the BBC retains its balance and its integrity, how it retains the trust of the British people and the licence fee payer, because, you know, that's absolutely fundamental for the future of the BBC.
"But actually it reflects upon us as a nation, because the BBC is such a well known and such a well respected brand around the world."
BBC chair Samir Shah is expected to apologise in a letter to Dame Caroline's committee later today.