The leader of the Australian Labor Party is refusing to provide proof of his citizenship status, fuelling speculation that he could hold dual citizenship with Britain.
Bill Shorten's father was born in England, but he told media over the weekend that he'd renounced his British citizenship years ago.
Despite this, Mr Shorten would not provide evidence to media and said "I don't feel any obligation to justify what I just said...because I know it to be true," ABC reports.
The citizenship crisis is continuing to disrupt Australia's parliament, a month after it began to unfold. In July two Greens senators resigned from the federal Parliament when it was revealed they were dual citizens - meaning they weren't qualified to be elected.
Prime Minister Malcolm Turnbull condemned them at the time, but since then three of his cabinet members have been dragged into the crisis. Last week it was revealed that Deputy Prime Minister Barnaby Joyce dual citizenship with New Zealand and he swiftly moved to renounce it.
Mr Turnbull's former Minister for Resources Matt Canavan had to step down from his position when it was revealed he held dual citizenship with Italy, and another Minister Fiona Nash holds dual citizenship with Britain.
It's also reported that One Nation senator Malcolm Roberts held dual citizenship with Britain when he was first elected to Parliament.
The Australian High Court will begin assessing the cases of numerous dual-citizen MPs later this week, as pressure to change the constitution continues to mount.