Mr Bercow - who retired as Speaker on October 31 - added that it was "better" for the country to remain in the EU.
The former House of Commons Speaker - who stepped down from the role last week after more than a decade - made the remarks during an event organised by the Foreign Press Association in London. "The foreign policy mistakes of the post-war period are my honest views".
"I respect Prime Minister Johnson but Brexit doesn't help us".
Giving away one of the worst kept "secrets" in parliament, Mr Bercow confirmed what most politicians believed to be his stance on the issue by saying the United Kingdom would be better off staying in the EU.More news: Pat Cummins rested from Perth, Andrew McDonald to start at the Gabba
He, however, rejected the idea he had blocked Brexit, insisting "it was Parliament" that had prevented Britain from leaving before now, "not me".
"Disgraceful this man was allowed to referee our Parliament for so long".
Meanwhile BBC political editor Laura Kuenssberg said: "This will only confirm what Bercow's critics always believed... and he still won't do any United Kingdom interviews so we can't ask him about it yet".
Mr Bercow also said, "with total certainty", Parliament would be debating Brexit for at least the next five years - if not the next 15 - and that was "blindingly obvious".More news: Lima Astronomical Society holding Mercury Transit viewing
None of the major parties are set to oppose Sir Lindsay Hoyle MP in the upcoming general election after he was voted in as the new Speaker of the House of Commons earlier this week..
Hoyle was elected speaker of Britain's House of Commons on Monday, chosen by lawmakers from among seven candidates to replace the influential but contentious Bercow.
Mr Bercow said: "I am not going to reveal for which party I will vote for".
The former deputy Speaker won the final round of voting with 325 votes against the 213 cast for fellow contender Chris Bryant.More news: Moody's cuts India's outlook to 'negative' over concerns of slowing economic growth
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