One Nation senator Malcolm Roberts during his Thursday night Sky News interview. He said he sent correspondence to British authorities on June 6 - three days before the cut-off for nominations - but did not clarify whether he went through the proper renunciation process required by the UK. Anne Twomey from the University of Sydney says Senator Roberts must clear up two pressing questions - when his renunciation took effect and exactly what steps he took before nominating to renounce. "It would be significant if that renunciation took effect after the nomination date. The legal status of renunciation is a matter of UK law - not a matter of what Senator Roberts 'chooses to believe'," Professor Twomey said. "The second question is whether he had taken 'all reasonable steps' to renounce his foreign citizenship before the nomination date. If there was a formal procedure to do so and he did not comply with that procedure before the nomination date then it is arguable that he did not take all reasonable steps."

Anne Twomey from the University of Sydney. Professor Twomey said declaring that he renounced his foreign citizenship on June 6 is not sufficient. "Combining these two issues - if, at the date of nomination, Senator Roberts was as a matter of UK law still a citizen of the United Kingdom and if, at that time, he had not taken all reasonable steps to renounce that citizenship as he had not complied with the legal procedure for doing so - then there is a good case to say he was in breach of section 44. It would be a matter for the High Court, however, to decide that." Fairfax Media put some of these questions to Senator Roberts' office but they have refused to answer. Senator Roberts' senior media adviser, Sean Black, threatened to report journalists to police.

"Your persistent emails, despite requests to stop, is classified by our office as stalking," Mr Black said in an email. "Any continued pestering or harassment from you or your colleagues of anyone, including me, from our office or organisation will be referred to the Queensland police. "This issue is now over. Stop the harassment. Please find another victim." In his interview, Senator Roberts said he wrote to the British authorities on May 1 last year to ask them whether he was a British citizen, given he was born to a Welsh father in India. He said he got no response so wrote further correspondence on June 6 - three days before nominations closed - saying that if he was a citizen he fully renounced. He subsequently nominated as a candidate and won a Queensland Senate seat.

It was not until December 5 that he got a response from the British High Commission confirming his citizenship was revoked. "I've taken all steps that I reasonably believe necessary," Senator Roberts told Sky News. Senator Roberts was born to an Australian mother and a Welsh father in India in 1955 and came to Australia when he was aged 7. He became an Australian citizen in 1974 and said he only ever travelled on his Australian passport. Loading He said he did not have any reason to believe he was a British citizen until he came to sign the nomination form last year and decided to double check.

Asked if he was confident he could resist any court challenge, Senator Roberts said: "Very confident, and I have received advice legally to the same effect. Very pleased with that advice."