Vajgl has said his decision was motivated by "eurosceptical views" expressed in the non-parliamentary party's ranks, but Zares denies his interpretation.

He also said he stood a better chance of being elected on his own than as the top name of a Zares ticket or a list backed by Zares.

Zares president Pavel Gantar said the party was a "critical European party" but did not harbour eurosceptic views.

Indeed, he said it remained committed to the EU project but was critical of the way the Council and the Commission were tackling the economic crisis.

Vajgl, a former diplomat and foreign minister, was the only MEP elected on the Zares ticket in the 2009 EU election.

The party has since dropped out of parliament and remains on the margins.