The European parliament has begun a probe after French far-right leader Marine Le Pen's voting card was used by a Dutch far-right colleague. Ballots in the Strasbourg parliament are strictly personal.
Dutch far-right lawmaker Marcel De Graaff faced possible fines or a temporary ban from parliament on Friday.
Len Pen, who anti-EU views often rile other parliamentarians, described de Graaff's use of her electronic card on Wednesday as a "blunder," but denied that she had authorized his voting on her behalf.
During an exchange on Thursday, German EU lawmaker Manfred Weber said the far-right's actions amounted to "insolence that cannot be surpassed."
"You face a major scandal here," said Weber who leads parliament's conservative EPP grouping.
Le Pen, in turn, said de Graaff had shown a "chivalrous spirit" by voting while she had stepped out of the chamber "for a few seconds."
At the time, parliament was voting over resolutions on EU strategy and relations with Balkans nations.
Parliament's administrative spokesman Jaume Duch Guillot said parliament President Martin Schulz would begin the probe by meeting de Graaff.
Ructions abroad and at home
In last year's European elections, Le Pen's National Front and other euroskeptic groupings scored gains.
Earlier this year, the European Parliament asked the EU's anti-fraud body OLAF to look into possible misuse of funds by the French National Front party.
At home in France, Le Pen has faced trial for comments she made five years ago comparing Muslim street prayers to foreign occupation.
ipj/kms (AP, dpa)