Former London Mayor Boris Johnson holds up a Cornish pasty during the launch of the Vote Leave bus campaign, in favour of Britain leaving the European Union, in Truro, Britain May 11, 2016. [Photo/Agencies]

LONDON - Former London mayor and leading Brexit campaigner Boris Johnson sparked fury Sunday after he compared the European Union (EU) to Adolf Hitler's Nazi Germany.

His remarks, viewed by Remain campaigners as inflammatory, fuelled a war of words in both camps, with some 'Leave' members of Prime Minister David Cameron's Downing Street cabinet leaping to Johnson's defense.

Johnson made his remarks in an article in the Sunday Telegraph in which he warned 'that while bureaucrats in Brussels are using "different methods" from the Nazi dictator, they share the aim of unifying Europe under one authority'.

Johnson said that the past 2,000 years of European history had been characterised by repeated attempts to unify Europe under a single government.

He says the EU's "disastrous" failures have fuelled tensions between member states and allowed Germany to grow in power, "take over" the Italian economy and "destroy" Greece.

"Napoleon, Hitler, various people tried this out, and it ends tragically. The EU is an attempt to do this by different methods. But fundamentally what is lacking is the eternal problem, which is that there is no underlying loyalty to the idea of Europe." said Johnson, adding : "There is no single authority that anybody respects or understands. That is causing this massive democratic void."

His comments led to an immediate row between anti- and pro-EU campaigners, with fellow Conservative and cabinet minister Chris Grayling saying: "Boris is a historian. He was doing a piece of historical analysis."

In a media interview in London later Grayling said he was concerned that if Britons vote to stay in the EU, "10 years down the road there are clear plans to create a federation in the Eurozone which will dominate, it will look like the United States of Europe".

Other senior Conservatives backing 'Brexit' also rallied to support Boris Johnson after the former London Mayor compared the European Union to Hitler's Nazi Germany.

Former Conservative Cabinet ministers Iain Duncan Smith and Lord Lamont, as well as Respected Conservative MP Jacob Rees-Mogg, defended Johnson's comments.

Johnson, seen by many as a successor to David Cameron as Conservative leader, put pressure on Cameron by challenging him to a face-to-face television debate.

Leading opposition politicians from the Labor party attacked Johnson's remarks. Hilary Benn, Labor's shadow foreign secretary, said Johnson's comparison of the EU to the Third Reich was "offensive and desperate".

Benn said: "Leave campaigners have lost the economic argument and now they are losing their moral compass. After the horror of the Second World War, the EU helped to bring an end to centuries of conflict in Europe and for Boris Johnson to make this comparison is both offensive and desperate."

Labor MP John Mann said Johnson should be sacked from the Vote Leave campaign, saying on social media Sunday: "Boris Johnson's absurd and offensive Hitler comments mean he should immediately be sacked from the leave campaign."

As the June 23 national referendum gets closer, both sides are expected to win supporters, with pollsters saying the in and out camps neck-and-neck.