Boris Johnson: The UK foreign secretary's biggest blunders

The pro-Brexit campaigner will now be making frequent appearances in Brussels. The euroskeptic wasn't always so adverse to European integration, whatever his EU opinions. In 1997, he said: "I'm rather pro-European ... I certainly want a European community where one can go off and scoff croissants, drink delicious coffee, learn foreign languages and generally make love to foreign women."

Guests at a gay rights event in 2013 walked out in disgust after Johnson said the following about gay marriage: "I’m delighted that as of this autumn any young man will be able to take his chum up the Arsenal ... and marry him." Labour's Angela Eagle, the first female MP to come out while in office, said that Johnson's "crass and tasteless remarks" only served to undermine the gay community.

Earlier this summer Johnson struck again, comparing the EU's aims to Hitler's. Speaking to UK newspaper "The Telegraph," Johnson said European history had seen repeated attempts to rediscover the "golden age of peace and prosperity under the Romans." "Napoleon, Hitler, various people tried this out, and it ends tragically. The EU is an attempt to do this by different methods," he said.

Born in New York, Johnson has upset the "special relationship" with the US more than once. In April, Johnson faced huge criticism after recounting the story of a bust of Winston Churchill being moved from the White House to the British Embassy. In the British tabloid "The Sun," Johnson asked whether the move was "a symbol of the part-Kenyan President's ancestral dislike of the British Empire."

But Johnson is no stranger to making derogatory comments. In his 2002 column, he described how the Queen had "come to love the Commonwealth, partly because it supplies her with regular cheering crowds of flag-waving piccaninnies." Commenting on then-Prime Minister Tony Blair's trip to Congo, Johnson wrote how "the tribal warriors will all break out in watermelon smiles to see the big white chief."

In November last year, Palestinian authorities canceled Johnson's visit after he said a boycott of Israeli goods was "completely crazy" and supported by "corduroy-jacketed, snaggle-toothed, lefty academics in the UK." Officials said Johnson's comments risked creating protests if he visited the West Bank, and accused him of adopting a "misinformed and disrespectful" pro-Israeli stance.

In 2008, Johnson even managed to offend his hosts at the ceremonial passing of the Olympic flag from Beijing to London. "I say this respectfully to our Chinese hosts, who have excelled so magnificently at Ping-pong," Johnson said. "Ping-pong was invented on the dining tables of England in the 19th century and it was called Wiff-waff!"

Johnson won a £1,000 prize in May for penning a poem about Recep Tayyip Erdogan, in which he referred to the Turkish prime minister as a "wankerer," rhyming with the Turkish capital, Ankara - a far cry from Johnson arguing that Turkey should join the EU in 2006. The competition was launched after Erdogan sued German comedian Jan Böhmermann, whose poem accused him of having sex with a goat.