The UN's human rights chief Zeid Ra'ad Al Hussein said a newspaper article in The Sun in which columnist Katie Hopkins compared migrants to cockroaches is reminiscent of Nazi propaganda.
In a statement, Al Hussein said that the Third Reich and those responsible for the Rwandan genocide of the 1990s likened their victims to animals or insects, and urged UK regulators to take action to curb "inflammatory" language in the media.
"The Nazi media described people their masters wanted to eliminate as rats and cockroaches," said Al Hussein.
"This type of language is clearly inflammatory and unacceptable, especially in a national newspaper. The Sun's editors took an editorial decision to publish this article, and – if it is found in breach of the law – should be held responsible along with the author."
In the statement, Al Hussein attacked coverage of immigration issues in the UK media, with Hopkins' language typical of "decades of sustained and unrestrained anti-foreigner abuse, misinformation and distortion".
In the April 17 column, published days before 800 migrants died when their boat capsized in the Mediterranean, Hopkins, a former reality show contestant, describes her lack of sympathy for those attempting to enter the EU illegally.
"No, I don't care. Show me pictures of coffins, show me bodies floating in water, play violins and show me skinny people looking sad. I still don't care," she said.
Hopkins added: "Make no mistake, these migrants are like cockroaches. They might look a bit 'Bob Geldof's Ethiopia circa 1984', but they are built to survive a nuclear bomb. They are survivors."
An online petition demanding The Sun remove Hopkins as a columnist has gained 284,000 signatures, and the Independent Press Standards Organisation said it had received 300 complaints against the article, and was investigating whether it broke the Editor's Code.
Al Hussein said that the UK tabloid media had a long history of whipping up anti-immigrant fears.
"This vicious verbal assault on migrants and asylum seekers in the UK tabloid press has continued unchallenged under the law for far too long," he said.
"I am an unswerving advocate of freedom of expression, which is guaranteed under Article 19 of the International Covenant on Civil and Political Rights(ICCPR), but it is not absolute. Article 20 of the same covenant says: 'Any advocacy of national, racial or religious hatred that constitutes incitement to discrimination, hostility or violence shall be prohibited by law.'"
He singled out the Daily Express for criticism.
"To give just one glimpse of the scale of the problem, back in 2003 the Daily Express ran 22 negative front-page stories about asylum seekers and refugees in a single 31-day period," he said.
"Asylum seekers and migrants have, day after day, for years on end, been linked to rape, murder, diseases such as HIV and TB, theft, and almost every conceivable crime and misdemeanour imaginable in front-page articles and two-page spreads, in cartoons, editorials, even on the sports pages of almost all the UK's national tabloid newspapers."
He said that although a similar process of demonization was taking place in other European countries, it was usually led by "extremist political parties or demagogues rather than extremist media".
He urged European countries to take action, and said that xenophobes, "under the guise of freedom of expression, are being allowed to feed a vicious cycle of vilification, intolerance and politicisation of migrants, as well as of marginalised European minorities such as the Roma".