Belgian MEP Guy Verhofstadt, currently running for the EU's top job for the liberal ALDE group, challenged Italian interior Minister Matteo Salvini to a debate on Monday accusing him of "being paid by Putin to destroy Europe."
"Just like you, your extreme right-wing friends, (France's Marine) Le Pen, (Austria's Heinz-Christian) Strache, (the UK's Nigel) Farage and (Hungarian Prime Minister Viktor) Orban are constantly plotting and paid by (Russian President Vladimir) Putin to destroy Europe," Verhofstadt said in a video posted on Twitter.
"Hereby I challenge you to a one-on-one debate, as people have the full right to know what devil's plan you have in mind.
"Tell me where you want to do it, in Brussels or in Italy. I will be there," he added.
Salvini and the representatives of nationalist parties from 11 EU countries, including Marine Le Pen who heads France's far-right Rassemblement National party, gathered for a rally in Milan on Saturday in a show of force ahead of the EU parliamentary elections held on May 23- 26.
Far-right and populist parties are expected to do well at the EU-wide ballot, potentially weakening the EU Parliament's main groups, including Verhofsdtad's centrist ALDE.