A UKIP MEP has been ejected from the European Parliament after directing a Nazi slogan at a German colleague.
Godfrey Bloom said "Ein Volk, ein Reich, ein Fuehrer" - one people, one empire, one leader - as Martin Schulz was making a speech.
He was ordered out of the chamber and will face disciplinary measures.
Mr Bloom told the BBC he stood by his words, describing the leader of the socialist group in the parliament, as "a national socialist".
Mr Bloom made the heckle as Mr Schulz, a member of Germany's Social Democratic Party and leader of the socialist bloc in the Parliament, was speaking during a debate on the economic crisis in the Irish Republic.
European Parliament president Jerzy Buzek, chairing the debate, looked set to carry on but jeers rose up and the French centre-right leader in the Parliament Joseph Daul challenged Mr Bloom to apologise.
He said: "We are in a democracy, this is a democratic era and I would ask you to make an official apology. This is not acceptable - I'm almost surprised you didn't add concentration camps to the equation."
The UKIP MEP stood up and replied: "The views expressed by Herr Schulz meet the case - he is an undemocratic fascist."
Amid a growing clamour from MEPs, Mr Buzek then asked Mr Bloom to leave the chamber.
Mr Bloom did so - only to return later to take part in a vote, when he clashed with replacement chairman Edward McMillan-Scott, a former Conservative member, who asked MEPs for a show of hands on whether Mr Bloom should be expelled and the majority agreed.
Mr Schulz, in a personal statement, dismissed Mr Bloom's "insult" saying "You have to have a certain degree of passion to your insults to affect me."
But he thanked MEPs from different parties for their messages of support, which he said was a demonstration of the democratic values that the "vast majority" of MEPs shared.
But UKIP leader Nigel Farage told MEPs that his eurosceptic group was angry about the "uneven" application of the Parliament's rules.
He claimed Mr Schulz had accused UKIP members and their fellow eurosceptics of "opening the door to fascism" by opposing the Lisbon treaty and that the co-president of the Green MEPs, Danny Cohn-Bendit had called them "mentally ill".
"Mr Schulz regularly calls people fascists and when he is called one the member in question is asked to leave. That isn't right. That isn't fair."
Mr McMillan-Scott rejected his complaint and suspended the sitting for five minutes, while Mr Bloom and a small group of MEPs were escorted from the chamber, to applause from some members.
Commenting afterwards, Mr Farage said: "Whereas we accept that Mr Bloom's jibe in the Parliament may have been rash and inflammatory, we fully support his sentiments about the formation of an undemocratic Europe."
Speaking afterwards Mr Bloom commented: "These Euro nationalists are a danger to democracy. These people are fanatics. People have got to wake up to this fact.
"My father, as a Spitfire pilot, fought for freedom against Nazi domination of Europe. As an MEP, I will fight against the destruction of democracy across Europe."
But his jibe did not go down well British MEPs from other parties.
Labour group leader Glenis Willmott said: "Once again, Ukip is trying to brew up a storm to make headlines back home. Godfrey Bloom's actions are an insult to all those who have fought against fascism."
Liberal Democrat group leader Fiona Hall described Mr Bloom as a "national embarrassment".
It is not the first time that Mr Bloom - who represents Yorkshire and North Lincolnshire - has courted controversy with his comments.
He has argued that man-made global warming is a myth and praised the sinking of the Greenpeace ship Rainbow Warrior in 1985, in which one man died.
In 2004, he said no "self-respecting" small business owner would employ a woman of child-bearing age.
UKIP has 12 MEPs in the European Parliament.