(JTA) — Former London Mayor Boris Johnson has come under fire for comparing the goals of the European Union to Hitler.

Johnson, who is in favor of Britain leaving the EU, told the Sunday Telegraph that the EU, like Hitler, aims to unify Europe under one “authority.”

“Napoleon, Hitler, various people tried this out, and it ends tragically,” the Conservative Party lawmaker told The Telegraph. “The EU is an attempt to do this by different methods.

British voters will cast ballots next month in a referendum on staying in or leaving the European Union. A vote to leave is being called colloquially “Brexit.”

As in elsewhere in Europe, Britain’s right-wing parties resent UK membership in the bloc. A Brexit would ensure Britain is not pressured into taking in some of the 1.8 million mostly Muslim migrants who entered Europe last year, they argue.

Prime Minister David Cameron is among those who wish to remain, but agreed to a referendum to appease his Conservative Party’s right-leaning bloc.

Johnson reportedly is a favorite to become the next leader of the Conservative Party.

The president of Britain’s Board of Jewish Deputies, Jonathan Arkush, said, “I don’t think references to Hitler in the debate on Britain’s position in the EU helps the arguments at all,” according to the Jewish Chronicle.

Labour Party lawmaker Yvette Cooper, who supports remaining in the EU, accused Johnson of using Hitler to play “nasty, nasty games,” according to the Chronicle. She said Johnson showed a “shameful lack of judgment” and was playing “the most divisive, cynical politics.”

“He should not try to play political games with the darkest and most serious chapter of Europe’s history,” Cooper said, adding: “The EU has played a critical role keeping peace in Europe ever since.”

The Labour Party in Britain has come under increasing attack in recent weeks for its perceived tolerance of members who make anti-Semitic remarks.