Manfred Weber delivers a speech during the European People's Party statuary Congress in Madrid in 2015 | Gerard Julien/AFP via Getty Images Manfred Weber calls for defunding of ‘neo-fascist’ political group European People’s Party leader says Alliance for Peace and Freedom is using funds to advance ‘extremist’ positions.

The leader of the European Parliament's biggest political group wants the assembly to stop funding a pan-EU party that he said brought together "the worst right-wing extremists and neo-fascists around Europe."

Manfred Weber, chairman of the European People's Party group, wrote to other parliamentary group leaders Tuesday saying the Alliance for Peace and Freedom, which received €600,000 in funding from the Parliament in 2016, had plans to use the money to regroup "some of the most radical and militant right-wing extremist parties."

Weber said the starting point for investigating how the group was using funds from the Parliament should be a political rally it plans to hold in Stockholm on May 28. The EPP chairman called on parliamentary leaders in the Conference of Presidents to discuss taking action to de-fund the group.

"We have to make sure that the European Parliament is making best use of its monitoring and control mechanisms in the run-up to the possible triggering of a de-registration procedure," Weber wrote. "We have to send a clear signal to the those extremists who are working against the very foundations of our society."

In the letter, he cited accusations against political parties in the group, including the alleged involvement of Greece's Golden Dawn party in the murder of an anti-fascist rapper and alleged anti-constitutional behavior by Germany's National Democratic Party, which is facing a ban by the German Constitutional Court.

Weber also called on Parliament Secretary General Klaus Welle to investigate if the party has been receiving money from countries outside of the EU and if it is directly or indirectly funding national parties or candidates.