French National Front leader Marine Le Pen has formed a political group of right-wing nationalist parties in the European Parliament, reports the BBC.
The anti-EU Europe of Nations and Freedom bloc includes Hungary's far-right Jobbik and the Freedom Party of Dutch politician Geert Wilders.
The grouping also has the support of UK MEP Janice Atkinson, expelled from UKIP in March over an expenses scandal.
Forming the group will give the MEPs more influence in the parliament.
It will also mean that the new bloc's members have access to millions of euros in extra funding as well as more staff and speaking time.
To be valid, a group needs 25 MEPs from at least seven different nationalities.
Mr Wilders, whose anti-Islam rhetoric has seen him face legal action, said that the formation was a "historic moment".
"Today it's the beginning of our liberation, our D-Day," he told reporters, adding that the new bloc would be the voice of the new "European resistance", defending their countries' sovereignty. The anti-Islam leader said the bloc would fight mass immigration as well as "Islamisation".
Eurosceptic and far-right parties made gains in last year's European Parliament elections, in what France's PM Manuel Valls called a "political earthquake".
Until now the far-right National Front (FN) has struggled to find members from enough countries to form a group.
But it secured support from MEPs in Italy's Northern League, Austria's Freedom Party, Vlaams Belang from Belgium and the Polish Congress of the New Right.