With less than six weeks to go before the so-called Brexit referendum in the United Kingdom takes place on June 23 when the country’s public will vote to decide whether it should continue to be a part of the European Union, the knives are out on both sides of the debate.

While most of the domestic establishment, including Prime Minister David Cameron, the Bank of England and various corporate heavyweights and even scientists, and international bodies such as NATO, the International Monetary Fund and the White House have thrown their weight behind the choice to stay, London’s former Mayor Boris Johnson, who last week made place for Sadiq Khan, is leading the campaign to leave.

And on Saturday, Johnson fired the latest salvo, when in an interview with the Telegraph newspaper, he said the idea of a unified Europe was inherently flawed, and had been proven so throughout history. Taking the argument a step further, he even compared the EU’s will with Hitler’s attempts to unify Europe.

“The truth is that the history of the last couple of thousand years has been broadly repeated attempts by various people or institutions – in a Freudian way – to rediscover the lost childhood of Europe, this golden age of peace and prosperity under the Romans, by trying to unify it,” Johnson told the newspaper. “Napoleon, Hitler, various people tried this out, and it ends tragically. The EU is an attempt to do this by different methods. But fundamentally what it is lacking is the eternal problem, which is that there is no underlying loyalty to the idea of Europe.”

The high-profile former mayor, widely seen as the leader of the “Leave” campaign, began a six-week tour of the country Saturday, exhorting voters to choose a U.K. outside the EU when the time comes.

“This [the referendum] is a chance for the British people to be the heroes of Europe and to act as a voice of moderation and common sense, and to stop something getting in my view out of control,” he said, adding that Winston Churchill — Johnson wrote a book about him — would have supported his campaign for the U.K. to leave EU.

The "Remain" campaign has been losing the lead it commanded in polls, and according to the BBC, various polls now give both sides a roughly equal chance at winning.