Madrid -- A Basque separatist leader has come out in support of a far-left party, which Spain's highest court has allowed to take part in the European Parliament elections.

The Supreme Court had initially disqualified the party, the Internationalist Initiative (II), from the June 7 polls, saying it was controlled by Batasuna, the banned political wing of the armed separatist group ETA.

But the constitutional court lifted the ban on Thursday, ruling there was insufficient evidence of the party's links to Batasuna to "justify the sacrifice of fundamental rights of political participation".

The former leader of Batasuna, Arnaldo Otegi, issued "a general call for support" of the II in the European elections "to require Europe's involvement in a democratic and peaceful solution to the Basque conflict."

The II "is not our party but holds our opinions," he told a press conference in the Basque city of San Sebastian.

Otegi was released from jail in August, 2008 after serving 14 months for glorifying terrorism.

Batasuna, banned since 2003 and with most of its leadership in jail, has had alleged proxies barred by the courts from running in the municipal elections of 2007, the legislatives of 2008 and the regional polls earlier this year.

ETA, considered a terrorist organisation by both the European Union and the United States, has killed 825 people in Spain in its 41-year campaign of bombings and shootings for an independent Basque homeland.

Batasuna was banned for failing to condemn ETA's violent tactics.

The 27 EU nations will elect 736 deputies for a five-year term at the parliament, which is the only directly elected EU institution and has an important role passing pan-European legislation.