Britain has protested to Hungary about a leaflet issued by the country's government claiming that parts of the UK are "no-go zones" because of the numbers of migrants.
The pamphlet - issued to millions of households as part of a referendum on EU migrant quotas - claims that there are several hundred no-go zones in European cities where the authorities are unable to maintain control and the host nation's social norms do not apply.
The supposed zones are not listed, but a map marks London out with a "no-go" sign, surrounded by five others which appear to relate to locations including Southampton and Peterborough. Elsewhere in Europe, Paris, Berlin, Marseille, Stockholm and Copenhagen are also marked out as cities with no-go areas.
The leaflet warns: "The so-called 'no-go' zones are areas of cities that the authorities are unable to keep under their control.
"Here the recipient society's written or unwritten norms do not apply. In those European cities, where immigrants live in great numbers, several hundred 'no-go' zones exist."
Challenged over the claims, Hungary's foreign minister Peter Szijjarto told BBC2's Newsnight: "We based this information on open, official reports given by the police of the respective countries and from the news.
"There are no-go zones in Europe and we don't want no-go zones in Hungary."
Mr Szijjarto said he personally "likes" London, but insisted that its designation as a no-go zone was made after consultation with the Hungarian embassy in the capital as well as "very careful" analysis of official reports.
Following its publication, the British Embassy in Budapest complained to the Hungarian foreign ministry about its contents.
Hungarian PM Viktor Orban is fighting for a No vote in the October 2 referendum on Brussels' plans to relocate migrants from frontline arrival states like Italy and Greece to other countries around the EU's Schengen zone.
The quota system would require Hungary to take in around 1,500 migrants.
But the leaflet accuses Brussels of trying to "prescribe the obligatory settlement of non-Hungarian citizens in Hungary" without the approval of its Parliament, and warns of the danger that terrorists might "slip in with the crowds of immigrants".
The row comes after a Chinese airline was forced to withdraw an in-flight magazine warning tourists to take precautions when visiting areas of London with ethnic minority populations.