The claims by Rep. Steve Scalise (R-La.) that he spoke at a gathering of white supremacists without knowing about the group’s affiliations are “not believable,” said Mark Potok, a senior fellow at the Southern Poverty Law Center.

Scalise should resign his position in the House GOP’s leadership, because his appearance before the group is “poisonous to any kind of real democratic process,” Potok said in an interview Tuesday.

This comes a day after Scalise acknowledged that he spoke to a convention of the European-American Unity and Rights Organization (also known as EURO) in 2002 while serving as a state representative. Scalise, 49, who is the third-ranking Republican in the House, has denied that he was involved with the group and said he did not know about its affiliation with racists and neo-Nazi activists.

“What is so off-putting about this is that the man was clearly pandering tot he most extreme kind of white supremacists and neo-Nazis as part of trolling for votes,” Potok said. “It just seems to me that this says something important about Steve Scalise. He was willing to go to a meeting of a group led by an infamous neo-Nazi and former Klan leader in the hopes that this would somehow help his political future.”

David Duke, the former Ku Klux Klan leader who founded EURO, said late Monday he didn’t know if Scalise knew what the conference was when he spoke. A longtime political adviser to Duke said Tuesday that Scalise did not know about EURO and said Scalise did not hear Duke’s remarks to the group.

Potok said it is hard to believe a Louisiana politician with national ambitions did not know about Duke or EURO.

“This was a group led by the best known white supremacist in America and comprised some of the best known activists in its leadership as well,” Potok said Tuesday. “So this was no secret.”

Duke’s group had appeared in national headlines not long before the conference, with stories about them in The Washington Post and USA Today, as well as local media reports about the convention itself. The Anti-Defamation League also listed this event on its calendar of extremist events in 2002.

The SPLC has been tracking EURO since it was founded under a different name in 2000. Potok said that the group was largely known for behind “Duke’s latest vehicle,” but he said it has not been very active in recent years.