Boris Johnson's controversial comments come less than six weeks before a referendum that will determine Britain's future within the EU.

"Napoleon, Hitler, various people tried this out, and it ends tragically," Johnson told British newspaper The Sunday Telegraph. "The EU is an attempt to do this by different methods," he added.

"But fundamentally what is lacking is the eternal problem, which is that there is no underlying loyalty to the idea of Europe," he continued. "There is no single authority that anybody respects or understands. That is causing this massive democratic void."

His comments were slammed by advocates of a unified Europe, who want Britain to stay in the EU.

US President Obama is among those warning against a "Brexit"

'Nasty, nasty game'

The Britain Stronger In Europe campaign was quick to react, with former cabinet minister Yvette Cooper of the Labour Party accusing Johnson of playing a "nasty, nasty game," the Press Association reported.

"The more he flails around with this kind of hysterical claim, the more he exposes his shameful lack of judgment," she was quoted as saying. "He should not try to play political games with the darkest and most sinister chapter of Europe's history."

Johnson, a member of Britain's Conservative Party, and a front-runner to succeed Prime Minister David Cameron, has become a leading voice of the "Leave" camp despite the fact that - or perhaps because of it - the government is advocating a "Remain" vote.

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The latest polls show the public evenly divided. According to the What UK Thinks website, the combined average of six recent polls show the electorate is at a 50-50 split.

Ominously, however, 45 percent said they trusted Johnson more than Cameron "to tell the truth about Europe," while just 21 percent said they trusted the prime minister over his right-wing rival.

The poll results come despite warnings from various financial and commercial institutions that a vote for Britain to leave, or Brexit, the EU has no upside and could be potentially catastrophic for the British economy.

Some fear that a British vote to leave the EU could spark similar votes elsewhere in the 28-nation bloc.

The referendum is scheduled for June 23.

bik/jlw (AP, AFP, Reuters)