Former Prime Minister of Australia Tony Abbott says opposition leader Bill Shorten needs to prove his citizenship or "shut up".
Mr Abbott is calling on Mr Shorten to publically renounce his British citizenship, by releasing evidence from British authorities.
SBS reported the former Prime Minister told reporters in Canberra on Monday, "I say to Bill Shorten show it or shut up".
Holding a letter from the British government, showing his own1993 renouncement of UK citizenship, he said "if you haven't got a letter, you are in exactly the same position that he is in, and you should let the parliament get on with its job this week".
Meanwhile, deputy Prime Minister Barnaby Joyce has insisted he has the right to remain in his role while the High Court decides on his future.
Disruptions are expected within parliament by the Labor party until either the National party leader stands down from cabinet, or the court makes its ruling.
But Mr Joyce said the tactics aren't helping the view of the opposition party to voters.
He said he would have stood down from his ministerial position if the government hadn't received strong advice from the solicitor-general.
Prime Minister Malcolm Turnbull will be heading to the Pacific Islands Forum in Samoa this week, and Mr Joyce will be acting Prime Minister, but Labour contends Mr Joyce is unfit to do so while his eligibility is in doubt.
Cabinet minister Fiona Nash's eligibility to sit in parliament has been referred to the High Court because of her dual citizenship.
In August it was found she held British citizenship, which under the constitution disqualifies election to parliament.
Attorney-General George Brandis said on Monday the government's view was that Senator Nash was ineligible to sit.