Mark Collett posted pictures on Facebook of his Vote Leave stall on Briggate and urged other “Nationalists” to do the same.
Mr Collett wrote on his Facebook page: “This is a pivotal moment in British politics and a real way Nationalists can get out and campaign for something worthwhile.
Vote Leave is the official campaign for a Leave vote in the upcoming referendum on Britain’s membership of the European Union.
A Vote Leave spokesman said: “He is not part of our campaign. We are a volunteer organisation, but anyone who is or was in the past a BNP campaigner is asked not to campaign for us or to distribute Vote Leave material.”
It has put a strong emphasis on street level campaigning but Mr Collett’s involvement will raise questions over the level of control it has over who has access to its materials.
The organisation said it would asked anyone with BNP connections to stop using its materials and there was “no place for the BNP in our campaign”.
Earlier this week, former London Mayor Boris Johnson, a leading figure in the Vote Leave campaign, suggested the European Union and Hitler had common aims in establishing a single European state but through different means.
Former York Council leader James Alexander, who highlighted Mr Collett’s activities in support of Vote Leave, said: “Boris Johnson should route out BNP sympathisers, Nazis and the far-right in the Vote Leave campaign before making historically illiterate comparisons.”