Far-right politician Gabor Vona addressed crowds at a rally in London on Sunday, despite protests from anti-fascist demonstrators.
Vona, the leader of the Hungarian political party Jobbik, spoke in front of a crowd of about 150 supporters in Hyde Park.
His original plan, to speak outside Holborn station in central London, was thrown into chaos when a crowd of 150 anti-fascist demonstrators gathered to deny him a platform.
Police prevented Jobbik supporters from leaving the station, forcing them to reconvene in Marble Arch and nearby Speakers' Corner, in Hyde Park.
Sabby Dhalu, joint national secretary of Unite Against Fascism (UAF), said: "UAF has played a central role in driving back fascism in Britain. Jobbik's fascist hatred has no place in a modern society here, or in the rest of Europe.
"Wherever fascists have a presence, racist, anti-Semitic and Islamophobic attacks increase. We call on all democrats to reject Jobbik this Sunday."
Vona, 35, and his Jobbik party have been accused of holding strongly anti-Semitic views, and of fuelling hatred against the Jewish and Roma communities in Hungary. The speech was planned for the day before UK Holocaust Memorial Day, to draw support from Britain's 50,000-strong Hungarian community ahead of elections in Hungary.
His party has been linked with alliances with other far-right parties across Europe, including the British National Party and Greece's Golden Dawn party.
His planned speech drew condemnation from anti-fascist campaigners. Last week a petition with 14,000 signatures was presented to Home Secretary Theresa May calling for Vona to be banned from entering the UK.
Vona has advocated segregation for Hungary's 800,000 Roma. His foreign policy spokesman Marton Gyongyosi has called for a register of Jewish people who, he claimed, pose a "national security risk". The party's paramilitary wing, Hungarian Guard, likened to the Nazi brownshirts for their habit of wearing black boots, was banned in 2009.
Jobbik is Hungary's third-largest political party, with 17% of the vote and nearly 50 seats in parliament. Vona has recently tried to distance himself from the racism allegations, saying earlier this month: "We've had enough of racism! There won't be a law in Hungary that would allow for a differentiation to be made on ethnic or religious basis between a human and another one. We want equality. Even the honest gypsy will do better if Jobbik gets to govern. Not because he is gypsy, but because he is honest."
However, Vona maintained his support for capital punishment and chemical castration for some criminals.