The UN human rights chief has accused US presidential candidate Donald Trump and Dutch nationalist Geert Wilders, among others, of spreading "humiliating racial and religious prejudice".
Zeid Raad al-Hussein said on Monday that "populist, demagogues and political fantasists" like Wilders and Trump, as well as Nigel Farage in Britain and Marine Le Pen in France, were using "fear" tactics similar to those of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS and Daesh).
"Make no mistake, I certainly do not equate the actions of nationalist demagogues with those of Daesh," the UN high commissioner for human rights, said at a gala dinner organised by the Hague-based Peace, Justice and Security Foundation.
"But in its mode of communication, its use of half-truths and oversimplification, the propaganda of Daesh uses tactics similar to those of the populists."
"And both sides of this equation benefit from each other - indeed would not expand in influence without each others' actions," he added, calling for global action to lessen the influence of populist politics that could turn violent.
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Zeid labelled Wilders' March 2017 election platform, which calls for no Muslim immigrants, the closing of mosques and the banning of the Quran, as "grotesque".
In a tweet, Wilders called Zeid, the son of a Jordanian prince and Swedish-born mother, "an idiot".
"The UN is grotesque," the Dutch right-wing politician responded. "Let's get rid of these bureaucrats."
Zeid said Wilders' rhetoric could have terrible consequences.
"History has perhaps taught Mr Wilders and his ilk how effectively xenophobia and bigotry can be weaponised," Zeid said. "The atmosphere will become thick with hate; at this point it can descend rapidly into colossal violence."
Zeid said discrimination was accelerating in workplaces, children were being shamed and shunned for their ethnic and religious origins.
"They are not 'really' European," Zeid said. "Entire communities are being smeared with suspicion of collusion with terrorists."
Zeid's speech drew a standing ovation from the crowd at the gala.