Former cabinet minister Matt Canavan will not vote in the Senate while the High Court decides on his citizenship.
The Senate has referred his case to the High Court to determine if he was ineligible because his mother nominated him for Italian citizenship when he was 25.
He has argued he could not renounce his Italian citizenship because he did not know his mother had registered him.
"Until three weeks ago, I had no knowledge or reason to believe that I may have been registered as an Italian citizen," he told the Senate.
"I was not born in Italy and neither were my parents.
" I do not believe that I have contravened section 44 of the constitution and my own legal advice indicates that I have a good case on this matter."
Senator Canavan said to respect the High Court process, he had decided not to vote in the Senate until the matter was decided.
Waters eyes comeback
The High Court will also deal with the cases of the former Greens deputies who both quit when they discovered they had dual citizenship.
However, Queenslander Larissa Waters is likely to make a comeback to the Senate.
The High Court is expected to decide that Ms Waters will be replaced in the Senate by Andrew Bartlett.
But Ms Waters has told colleagues she has "unfinished business that she wants to continue" and she will renominate at some stage.
She said her first priority was to help her party win a seat at the state election, due by May next year.
She has renounced her Canadian citizenship, meaning she is eligible to return to Parliament if chosen by her party when pre-selections open.
The other former Greens deputy leader, Scott Ludlam, also quit when he found he had dual citizenship with New Zealand, but he will not be seeking to run again "in the foreseeable future".
His case will also be referred to the High Court today and a recount is almost certain to mean Jordon Steele-John is chosen to replace him.
