"I want an audit", Mr Xenophon told FIVEaa's Leon Byner on Friday.
Like Deputy Prime Minister Barnaby Joyce, who is a New Zealand dual citizen, Nash said she would continue in her position until the High Court clarifies a section of Australia's constitution.
One list, published by the Australian, named 50 MPs who had at least a grandparent born overseas.
He went on to explain that it's not about using those rights and privileges of a foreign power as you only need to be entitled to those rights and privileges.
Australian Prime Minister Malcolm Turnbull convened an urgent cabinet meeting just after 6pm, where it was decided, based on advice from the Solicitor-General, that Nash did not have to resign from either the Senate, or lose her cabinet spot as minister for rural health.
Parliament's sitting week had ended, and it was too late for the Senate to refer her to the High Court.
Xenophon told Fairfax Media that he hoped to receive legal advice by Saturday.
The Greens and independents have called for an audit of all parliamentarians, but the major parties are not interested.
Fiona Nash admits she is a British citizen by descent, becoming the third Australian government minister caught in the country's dual-citizenship crisis.
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This means that both the Nationals' leader and deputy leader will be before the High Court to determine whether they are ineligible to sit in parliament.
Along with Xenophon and Nash, the freaky mess around section 44 of the constitution has ensnared deputy prime minister Barnaby Joyce, One Nation senator Malcolm Roberts and Nationals senator Matt Canavan.
"As Senator Nash admitted, she has known since Monday that she was a dual citizen, yet waited until one minute before the Senate rose for a two-week break to inform the parliament", Senator Gallagher said.
What's the problem? How can the court help?
The dual citizen MPs will get their first hearing before the High Court next Thursday.
The 116-year-old section of the Constitution that bans dual nationals is taking an extraordinary toll on the finely balanced Parliament elected in July last year.
Nash's case illustrates how far section 44 (i) can reach. Now, however, it has produced an unprecedented political and constitutional crisis. Now the government's situation has become so precarious that it will try to keep Joyce and Nash in their posts until the country's supreme court rules on their cases.
The constitution can not be changed without a referendum, which rarely succeed.
The Prime Minister can ask the Governor-General to discontinue the session of Parliament, but at this point it's unlikely he'd want to do that.