John Bercow is facing mounting pressure over allegations of bullying after one of Parliament's most senior former officials said his behaviour "terrified" staff and was "unworthy of someone in such public office".
David Leakey, who retired as Black Rod last year, said the Speaker had subjected him to "intolerable" rudeness while in office and accused him of "explosive and intemperate behaviour" towards his colleagues.
Allegations that Mr Bercow bullied two former aides "risk bringing Parliament into disrepute", Mr Leakey claimed, in a highly unusual intervention, which casts further doubt on Mr Bercow's future as Speaker.
It comes as Downing Street backed calls for a full investigation into bullying in Parliament, after former private secretary Angus Sinclair claimed Mr Bercow had verbally abused him and smashed a phone on a desk in a fit of rage. Mr Bercow strenuously denies any allegations of bullying.
Mr Leakey told PoliticsHome: "On one occasion he quite suddenly erupted in a rage, banging the table and being extremely and personally rude to me, including calling me an antisemite.
"He did apologise to me for that specific remark afterwards, but not for his other highly personal insults, and it is intolerable.
"His rage erupted, as on a previous occasion, and the red mist suddenly descended - it was quite disproportionate and unreasonable by any standards.
"His explosive and intemperate behaviour is legendary, objectionable and unworthy of someone in such public office – conduct which may not stand up to the standards expected in public life. There were lots of people who were, frankly, terrified of the Speaker."
Mr Leakey, whose role gave him responsibility for maintaining order in the House of Lords, said the row could bring Parliament "into disrepute" if it was not properly resolved.
A spokesman for Mr Bercow's office said the pair had had fundamental disagreements but the Speaker "refutes all the allegations levelled by Mr Leakey".
"John Bercow and David Leakey are two very different people with very different backgrounds, perspectives and ideas," the spokesman said.
"They had fundamental disagreements in 2011 and 2012, but interacted adequately after that."
Speaker’s Chaplain Rev Rose Hudson-Wilkin stepped in to defend Mr Bercow amid claims that a “frenzy” was being whipped up against him.
She told BBC's Daily Politics: “It feels like a frenzy at the moment and that concerns me.
"Not only in relation to Mr Bercow but in terms of other MPs there are times when a frenzy is whipped up around individuals and that quite concerning in terms of their wellbeing.”
Rev Hudson Wilkin questioned the motives of those criticising the Speaker, who she said was "not an establishment figure, let's put that out there".
She added: "The John Bercow that I know, and have been in pastoral care for - as I do with many others - is someone who is very kind, caring and compassionate.
"And I know that if he felt that he had done something to someone, that he would be mortified."
The row emerged when Mr Sinclair, a former aide, claimed the Speaker had sought to undermine him through mimicry, verbal abuse and angry outbursts. In one extreme incident, Mr Bercow allegedly smashed a mobile phone on his desk in a fit of anger.
The senior official - who worked for former Commons speaker Michael Martin until Mr Bercow took up the post in 2009 - said he was given “compulsory early retirement” in 2010, with an £86,250 pay-off preventing him from making complaints about his treatment in the House.
His successor Kate Emms also claimed to have been bullied by Mr Bercow. Colleagues previously told Newsnight that she had been diagnosed with post traumatic stress disorder.
An inquiry has already begun, under Dame Laura Cox QC, into claims of bullying by MPs. However it will not consider historical cases, including allegations against Mr Bercow.
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