Crossbench senator Nick Xenophon is making enquiries with the British Home Office after questions were raised about whether he picked up British citizenship by descent through his father.

If Xenophon is considered to have been a dual citizen at the time of the election, he may be ineligible to sit in the parliament.

According to ABC News, Xenophon's father Theodoros was born in Cyprus and came to Australia as a British citizen in 1951.

"This really is turning into a train wreck for the federal parliament," Xenophon said at a press conference on Friday morning. "No wonder Australians think so little of politicians because of this ongoing train wreck.

"I am doing all I can to clarify and sort it out."



Xenophon is the head of a group of three senators which plays a crucial role in the government passing legislation in the Senate.

The news came less than 24 hours after deputy Nationals leader Fiona Nash stood up in the Senate to announce that she unknowingly had British citizenship through her Scottish father.

Along with Xenophon and Nash, the bizarre mess around Section 44 of the constitution — which bans dual citizens from siting in parliament — has ensnared deputy prime minister Barnaby Joyce, One Nation senator Malcolm Roberts and Nationals senator Matt Canavan.

The only politicians to resign over their citizenship eligibility are Greens senators Scott Ludlam and Larissa Waters.

But Xenophon said Section 44 had shown itself to be "imprecise".

"It’s been around for 116 years but it seems the law is still evolving."

The dual citizen MPs will get their first hearing before the High Court next Thursday.