The leader of the No to Nice campaign has said he had no indication that he was dealing with racists when he attended meetings of Germany's extreme right wing National Democratic Party.
Justin Barrett told RTÉ he saw nothing that would suggest it was a Nazi or even a far-right organisation.
Mr Barrett confirmed that he attended and spoke at conferences organised by the National Democratic Party, but said he was only attending the meetings in his capacity as a member of the pro-life movement.
However, the Irish Alliance for Europe has said that Mr Barrett's comments on his trips to Germany have no credibility.
In a statement the group said that not alone was Mr Barrett a guest of honour at an NPD rally in Bavaria in May 2000 but that in 1999 he had attended the conference of the party's youth group - Young National Democrats.
Fianna Fáil has said that Mr Barrett must be either naive or else he expects Irish people to be gullible.
The Labour leader, Ruairi Quinn, has called on Mr Barrett to clarify the nature of his contacts with the organisation.