Geert Wilders and Marine Le Pen were among the politicians to attend a controversial summit in the Czech Republic, which was met by protestors outside.
The meeting took place at a hotel in Prague, which was heavily guarded with specialist security forces during over the weekend.
Mr Wilders, leader of the anti-EU, anti-migrant Party for Freedom in the Netherlands, said a “wall” needed to be built to stop “mass migration”.
After dodging protestors outside who booed and chanted against the far-right groups, Mr Wilders claimed the Czech Republic highlighted the problem facing the bloc.
He said: “In 30 or 50 years, the Czech Republic will be surrounded by countries with population where 20 percent of people will be Muslims.
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“That is as if the Czech Republic became a Gaza Strip. We need to prevent mass migration even if we should build a wall.”
Ms Le Pen, president of the National Front in France, also hit out at the EU – who she accused of threatening the very existence of Europe.
The failed French presidential candidate said: “Because we like Europe, we say that the EU is going to kill her.
“We are patriots – we defend our sovereignty.”
Protestors had gathered on the day of, and the night before, the event, which was hosted by the Czech Republic’s anti-Islam Freedom and Direct Democracy Party.
A group of several hundred protestors had gathered in the centre of Prague on Friday night and Saturday. The whistled and booed as attendees arrived at the event over the weekend.
The event was also slated by mainstream Czech politicians, with one party leader condemning the group as “extremists that threaten the interests of both the Czech Republic and Europe”.
The Czech Republic, despite the tone of the event, is home to as few as 5,000 Muslims. The country has also only accepted 12 asylum seekers and has refused to accept the EU’s migrant quota scheme.
The country, along with Poland and Hungary, could be taken to court by the union for failing to take part in the scheme.