Ex-London Mayor Boris Johnson has compared the European Union’s aims to those of Adolf Hitler, arguing that the 28-nation bloc is creating a superstate that mirrors the attempt of the Nazi leader to dominate the European continent.

Johnson, the most prominent political figure arguing that Britain should leave the EU, says the past 2,000 years of European history have been dominated by doomed attempts to unify the continent and recreate the Romans’ golden age.

“Napoleon, Hitler, various people tried this out, and it ends tragically. The EU is an attempt to do this by different methods,” he was quoted by The Sunday Telegraph as saying. “But fundamentally, what is lacking is the eternal problem, which is that there is no underlying loyalty to the idea of Europe. There is no single authority that anybody respects or understands. That is causing this massive democratic void.”