Australia's dual citizenship parliamentary crisis sparked calls for a nationality audit on Wednesday of all federal lawmakers as investigations continued into decisions made by ministers found to have been ineligible for their elected positions.

Australia's High Court on Friday disqualified five lawmakers because they were citizens of both Australia and another country, a breach of an obscure clause in the constitution that only came to light in July.

Two other parliamentarians had already resigned, while Australian Senate President Stephen Parry said he will resign after receiving confirmation he that is a UK dual citizen, BBC reported on Wednesday.

According to BBC, Parry said in a statement that he believes he was wrongly elected because of his dual nationality status.

The senior government figure said he was making the announcement with "a heavy heart" after receiving confirmation from the British Home Office, BBC reported, adding that Parry had inherited British citizenship from his father.

On Wednesday, Liberal member of Parliament Craig Kelly broke ranks with the government to support calls for the Australian Electoral Commission to audit the backgrounds of all federal lawmakers, as Acting Prime Minster Julie Bishop said she could not rule out more casualties.

“I think the best way to bring this to a head, to draw a line in the sand, let's have a full audit of everyone's record, put this behind us and move on and then, going forward, everyone will be crystal clear what the rules are,” Kelly told the Australian Broadcasting Corporation.

Richard Di Natale, leader of the minority opposition Greens party, supported the call, saying there was “a huge shadow over Parliament” eroding people's faith in democracy.

“It's no longer a happily stable Parliament we're entering constitutional crisis territory here,” he told ABC radio.

Concerns continue that more lawmakers will be exposed due to the multicultural makeup of Australia, where almost half the population are immigrants or have an overseas-born parent.

Bishop told Channel Nine TV that while no other lawmakers had raised concerns with her, it would be left to political parties to “just deal with the situation as presented to us.”

Bishop also said Australia's Attorney-General George Brandis was examining “a few” ministerial decisions made by two disqualified lawmakers, Barnaby Joyce the former deputy prime minister and leader of the Liberals' junior coalition partner, the National Party and his Nationals deputy Fiona Nash.

The opposition Labor Party had asked the government to release a list of questionable decisions made by the two ministers, saying it has received legal advice decisions made by them since last year's election could be open to challenge as they had been ineligible to run for Parliament.

Joyce, having renounced the New Zealand citizenship inherited through his father, will contest his seat again in a Dec 2 by-election.