The independent expert panel upheld earlier findings by Parliamentary Commissioner for Standards Kathryn Stone that Bercow had bullied members of his staff.
It said he should never be granted a parliamentary pass, which gives access to the building for MPs, staff and journalists, and that if he was still a member of parliament he would have been expelled.
Bercow, who joined the Labour party in 2021, became an international celebrity during the UK's bruising political wrangles over Brexit as he oversaw fractious debates with bellowing cries of "Or-derrrr!".
Bercow, the 157th House of Commons Speaker, transformed the centuries-old role, whose powers include running Commons business, overseeing votes and ruling on questions of parliamentary procedure.
His activist interpretation of the role and moves to allow MPs to challenge the government's decisions made him a hero to opponents of leaving the European Union, a villain to Brexit advocates and a thorn in the side of the Conservative government.
He also angered some by saying in 2017 that then-US president Donald Trump should not be allowed to address parliament, an honour given to some of his predecessors.
Bercow stepped down in 2019 after a decade as Speaker.
In its report, the panel said "it is for historians to judge whether the respondent was a successful reforming Speaker of the House of Commons".
But it said he was "a serial bully" whose behaviour "was so serious that, had he still been a Member of Parliament, we would have determined that he should be expelled by resolution of the House".
The panel upheld 21 allegations against Bercow by three current and former Commons staff members.
It said Bercow's behaviour, which included belittling staff, abusive language and in one case throwing a mobile phone "had no place in any workplace".
Bercow condemned the conclusions as a "travesty of justice" and said he had been subjected to a "vengeful vendetta".
"This has been a protracted, amateurish and unjust process which would not have survived five minutes' scrutiny in court," Bercow said.
"To describe what I have experienced as a kangaroo court is grossly insulting to kangaroos."
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