Former Mayor of London Boris Johnson | Charles McQuillan/Getty Images Boris Johnson compares EU to Nazi superstate He said: Napoleon and Hitler tried to dominate the continent. ‘The EU is an attempt to do this by different methods.’

Boris Johnson has mentioned before that the European Union is becoming a superstate, infringing on Britain's autonomy. On Sunday, the Brexit campaigner has compared the EU's aims to unify the continent to Hitler's efforts to dominate Europe.

Speaking in an interview with the Sunday Telegraph, Johnson said the past 2,000 years of European history had been marked by doomed attempts to unify the continent and recreate the “golden age” of the Romans.

“Napoleon, Hitler, various people tried this out, and it ends tragically. The EU is an attempt to do this by different methods," Johnson said.

Johnston also said that Europe lacks "underlying loyalty to the idea of Europe" and that "there is no single authority that anybody respects or understands."

These comments came as UKIP leader Nigel Farage backed Johnson to succeed David Cameron as Conservative leader if Britons vote to leave the EU in the June 23 referendum.

Farage leader described himself as a “Boris fan,” comparing him to former U.S. president Ronald Reagan.

Building on tensions on Britain's fate in or outside of the EU within the Conservative party ahead of referendum, Farage also said he could even envisage a situation in which he would work for Johnson in the government.

"Could I work for him? Yes. Could I see a scenario if he was PM and he asked me to do something? I wouldn’t rule it out,” Farage said.

Speaking to the Mail on Sunday, Farage also rejected suggestions that Johnson would not be serious enough to be prime minister if Cameron were forced to stand down. “Could he do it? Yes. If you’d asked me six months ago, I’d have said no, but I’ve changed my mind,” he said.