John Bercow is facing fresh pressure to quit today after another former senior Parliamentary official accused him of 'intolerable' behaviour.
David Leakey, who was Black Rod until last year, said the Speaker's tendency to fly into a rage was 'legendary' and he 'terrified' staff.
Revealing that he personally experienced an 'eruption' of Mr Bercow's temper, he branded him 'unworthy' of holding the historic role in the Commons.
The intervention by Mr Leakey, in an interview with The House magazine, will ramp up speculation over whether the Speaker can stay in post.
Commons chaplain Rose Hudson-Wilkin took to the airwaves to defend him this afternoon, saying that politicians were in a very 'pressured environment' and suggesting Mr Bercow suffered as he was 'not an establishment figure'.
He faced an open call from an MP to quit yesterday after his former private secretary accused him of foul-mouthed tirades and attempts at physical intimidation.
Other MPs privately say there is a growing feeling the position of the Speaker - who denies the claims - is hard to sustain.
They point out that he pledged on being elected in 2009 to stand down this year after nine years in the job - but has since reversed the pledge.
'He should go when he said he would,' one Tory MP said. 'If he doesn't things will only get worse.'
The Commons Speaker signalled defiance today as he was challenged by MPs over Angus Sinclair's claim that he was the victim of angry outbursts, foul-mouthed tirades and mimicry
Former Black Rod David Leakey (pictured left with Mr Bercow last year) said the Speaker's tendency to fly into a rage was 'legendary' and he 'terrified' staff
Other MPs like Conservative MP James Duddridge said he should resign on June 22 as it would be exactly nine years since his appointment.
'He should stick to his initial commitment to step down by the 22nd June,' Mr Duddridge said.
In a June 2009 letter to colleagues asking them to elect him, Mr Bercow promised to step down after that time had passed from his appointment.
'I believe strongly that the post of speaker should not be a job for life but an opportunity to make a difference within a reasonable period of time,' he wrote.
'If you do me the honour of electing me, I will serve for no longer than two full Parliaments and, in any event, for no more than nine years total.'
Angus Sinclair, who said he was repeatedly undermined by Mr Bercow, finding himself the victim of angry outbursts, foul-mouthed tirades and mimicry
Commons chaplain Rose Hudson-Wilkin told the BBC's Daily Politics that she did not know whether the allegations were true, but stressed politicians were under constant pressure and suggested Mr Bercow suffered because he is 'not an establishment figure'
Angus Sinclair said he was forced into early retirement with an £86,250 pay-off on condition he did not make any complaints.
Mr Bercow has denied behaving inappropriately, and insisted the 'great majority' of his former staff had left 'on perfectly amicable terms'.
Downing Street responded by calling for a 'proper investigation' – and twisted the knife by outlining three ways in which this could be carried out.
Mrs May's official spokesman suggested an existing inquiry into Commons bullying, , chaired by Dame Laura Cox, should have its remit widened to allow it to look at individual cases such as allegations against the Speaker.
'The Prime Minister has been very clear from the start that there is no place for bullying or harassment of any kind in the workplace, including Parliament,' he said.
'It is a matter for Parliament to decide how to proceed, but the latest allegations are concerning and should be properly investigated.'
Andrea Leadsom, the Leader of the House, also called for the inquiry's remit to be expanded, saying: 'We must call out unacceptable behaviour.'
However, it is understood that Dame Laura is not minded to expand the terms of her inquiry. It is unclear how any of the other allegations can be investigated, as at the time MPs were not accountable for behaviour towards Commons staff and the code of conduct was narrowly drawn.
Mr Bercow has faced previous bullying claims after Kate Emms, Mr Sinclair's successor as private secretary, was diagnosed with post-traumatic stress disorder after less than a year of working for him.
It his interview, Mr Leakey said the Commons Speaker was 'genuinely intimidating'.
'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 anti-Semite. He did apologise to me for that specific remark afterwards, but not for his