SYDNEY (AP) — Australia's dual citizenship parliamentary crisis deepened on Wednesday with a senior member of the ruling Liberal Party resigning, as calls grew for a nationality audit of all federal lawmakers and 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.

On Wednesday, the saga claimed its first victim from Prime Minister Malcolm Turnbull's Liberal Party in Senator Stephen Parry.

Parry had on Tuesday contacted British Home Office officials, who a day later confirmed he held dual citizenship because his late father had been born in the United Kingdom, after which Parry resigned his Senate seat.

There had previously been disquiet concerning the issue between the Liberal Party and its junior coalition partner the National Party over the latter's allegedly loose vetting systems on checking the nationality status of its electoral candidates. But not only is Parry the first Liberal Party member brought down in the crisis, he ranks as a party heavyweight, owing to his appointed position as president of the Senate, the upper house equivalent to the speaker of the lower chamber, the House of Representatives.

Parry wrote a letter to his fellow senators on Wednesday saying since the High Court's ruling had clarified the application of the relevant section of the constitution, he would "submit my resignation as both president of the Senate and as a senator for Tasmania to his excellency the Governor-General tomorrow."

Critics have condemned as outdated the 116-year-old constitutional ban on lawmakers having dual citizenship in a country where almost half the people are immigrants or have an overseas-born parent.

Also on Wednesday, Liberal Party lawmaker 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 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.