Under-fire John Bercow has been given support by a former colleague who suggested bullying allegations against the Commons Speaker may have been "people settling old scores".
The Speaker has denied allegations of bullying made against him by two former members of staff, but pressure has mounted on him with some MPs suggesting he should stand down.
There have been calls for parliament's standards watchdog to examine the Speaker's actions.
But Robin Fell, who served as principal doorkeeper in the Commons, said he had never experienced any bullying behaviour from the Speaker.
"My dealings with him have always been absolutely wonderful but he does have the reputation that he doesn't suffer fools gladly," he said,
"It's always been my experience that if you are dealing with someone who you think may not suffer fools gladly, it's probably quite a good idea not to be a fool."
Asked about the allegations, Mr Fell told BBC Radio 4's Westminster Hour: "Perhaps people are settling old scores that they didn't feel they could settle at the time, I don't know."
He added: "I have seen him cross when he is perfectly entitled to be cross.
"He sits at the top of a very large and prestigious organisation, the House of Commons.
"It's a stressful job."
Tory MP Paul Scully said the "inconsistency" of Mr Bercow's moods frustrated MPs.
He told Westminster Hour: "There are some days he could probably do with taking the medicament he prescribes backbenchers every other Prime Minister's Questions himself.
"I think he needs to be aware of what people are thinking and be open - these are serious allegations and I think rather than necessarily trying to close them down, be open, be upfront and say, 'OK, fine, investigate and see what you find'."
Tory MP Andrew Bridgen, a longstanding critic of the Speaker, has written to Kathryn Stone, the Parliamentary Commissioner for Standards, asking her to investigate whether Bercow has breached Parliament's code of conduct.
In the letter, reported by The Sunday Times, he wrote: "As Parliament seeks to address a culture of bullying and harassment ... it appears wholly inappropriate to allow allegations against the Speaker, who has himself called for a zero-tolerance approach to the issue, to go unaddressed."
Mr Bercow has strongly denied bullying allegations from former private secretaries Angus Sinclair and Kate Emms.