One Nation senator Malcolm Roberts is under mounting pressure to prove he's eligible to stay in Parliament but is refusing to provide evidence he renounced his British citizenship before last year's election.
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Despite previously insisting he has only ever held Australian citizenship, Senator Roberts - who was born in India to a Welsh father, potentially making him a British national by birth - now says he is "no longer a British or Indian citizen" and has "renunciation documents".
Senator Roberts has signed a statutory declaration that he is "a citizen of Australia only", and holds neither British not Indian citizenship. It also says that prior to becoming a One Nation candidate he "investigated" his eligibility under section 44 of the constitution, which has already caught out three senators this month.
But the statutory declaration does not specify whether Senator Roberts fully renounced his British citizenship before nominating, and he is resisting media and public pressure to release the primary documents from Britain.
Fresh questions were raised on Wednesday after Buzzfeed News published old travel documents that appear to confirm Senator Roberts travelled under a British passport as a child.
Despite the doubts about his own eligibility, Senator Roberts is leading calls for a review or inquiry into the dual citizenship eligibility of all MPs. He has written to Speaker Tony Smith and Senate President Stephen Parry asking them to investigate.
Senator Roberts' office refused to answer further questions on Wednesday but he tweeted: "Prior to nominating for the Senate I ensured that I was no longer a British or Indian citizen and have necessary documents."
In a separate post on Facebook he said: "Until the inquiry, my stat dec stands. My renunciation documentation will be provided to this inquiry."
But that appears to contradict what his office said last year. Asked about his citizenship status in October, a spokesman for Senator Roberts told Guardian Australia he had only ever held one citizenship.
"Senator Roberts has never held any other citizenship other than his Australian citizenship," the spokesman said. "He's had to obtain visas when he's travelled to the United Kingdom and to India, and people who are citizens do not have to get visas."
On Facebook, Senator Roberts also pointed out that if his stat dec is proved to be false statement it would be punishable by four years in jail.
Section 44 requires a parliamentarian to have taken all reasonable steps to renounce themselves of foreign citizenship to be eligible.
If Senator Roberts' election was ruled invalid his seat would likely go to the third person on One Nation's Queensland ticket, Fraser Anning.
Fellow One Nation senator Brian Burston, perhaps unaware of the lingering questions about his colleague, took to social media on Wednesday to declare "time is running out" for MPs born overseas to provide evidence of their sole citizenship.
"It shouldn't be too difficult. After all, they would have had to have it when they nominated for candidacy of their respective parties or for the AEC if they were independents," Senator Burston wrote on his official Facebook page.
"Perhaps, when we've cleaned out those whose loyalty is not entirely to this country we can start getting things fixed."