Matt Canavan discussed taking out Italian citizenship with his family in 2005 but says he never signed any documents or forms and believed the matter never progressed.

Deputy Prime Minister Barnaby Joyce on Wednesday defended the former resources minister as an "exemplary person" and said Senator Canavan's mother was "at her wits' end" that her son's promising political career had stalled.

Senator Canavan resigned from the Turnbull government ministry on Tuesday night after publicly declaring his mother signed him up for Italian citizenship without his knowledge.

Asked how that could happen given the rigorous application progress required to obtain Italian citizenship, Mr Joyce said: "Well, Senator Canavan has stated to me that he did not complete any forms, so it was a discussion the family had and he thought that's where it's rested. I think they've found the forms and they're unsigned."