A former private secretary to the speaker, Angus Sinclair, told BBC2’s Newsnight that Mr Bercow undermined him by mimicking him, swearing and shouting and that he once smashed a mobile phone by throwing it on the desk in front of him.
The Speaker’s office issued a firm denial of the allegations, which come as an independent judge-led inquiry is conducted into claims of bullying of staff in the Palace of Westminster.
Dame Laura Cox’s investigation was commissioned following an earlier Newsnight report alleging that clerks and other officials were bullied by MPs, including Mr Bercow.
Mr Sinclair was private secretary to Mr Bercow’s successor Michael Martin and retained the position when the new speaker took over in 2009.
He told Newsnight that Mr Bercow undermined him in front of other staff, shouted, swore and attempted to physically intimidate him.
The speaker was prone to “over-the-top anger”, he claimed, adding: “I’m not sure he was completely in control of it. The arms would wave around.”
He said: “There was one afternoon I was working at my desk and he came in and was absolutely furious about something.
“There was a lot of bad language and suddenly his mobile phone which he’d been holding was flung on the desk in front of me and broke into a lot of bits.”
Following the 2010 general election, he said the speaker told him he was no longer needed.
He said he was given “compulsory early retirement”, with an £86,250 payoff dependent on him signing a non-disclosure agreement barring him from making complaints about his treatment in the House.
Newsnight has previously reported that his successor Kate Emms was allegedly bullied by the speaker – a claim Mr Bercow denies.
Mr Sinclair said he felt that if he had not signed the non-disclosure agreement, but had instead put in a complaint, she may not have been put in that position.
“What I’d done was sign a cover-up and in a cynical way, I’d been paid to do it, and that’s not a good feeling,” he said.
A spokesman for the speaker’s office said: “Mr Speaker strenuously denies that there is any substance to any of these allegations.
“Mr Speaker has a superb team of dedicated, effective and long-serving staff – five of whom have worked for him very happily for a combined total of over 40 years.”