The leading pro-Brexit voice for the "Vote Leave" camp made references to the Nazi leader as well as Napoleon as having failed at European unification.
"Napoleon, Hitler, various people tried this out, and it ends tragically. The EU is an attempt to do this by different methods," Johnson told The Sunday Telegraph.
"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," Johnson said.
"The Italians, who used to be a great motor-manufacturing power, have been absolutely destroyed by the euro - as was intended by the Germans. The euro has become a means by which superior German productivity is able to gain an absolutely unbeatable advantage over the whole eurozone.
More From This Section
"This 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," Johnson said.
"He should not try to play political games with the darkest and most serious chapter of Europe's history. The EU has played a critical role keeping peace in Europe ever since," Cooper said.
With opinion polls suggesting the contest is close, leaders of all the main political parties are coming out strongly with both the Leave and Remain arguments.
British Prime Minister David Cameron warned yesterday that a vote to leave the EU in the referendum on June 23 would deliver an "immediate and sustained hit" to the economy that could tip Britain back into recession.