Deputy Nationals Leader Fiona Nash will be referred to the High Court after receiving advice that she is a British citizen.
Yet another federal government minister will be referred to the High Court after Deputy Nationals leader Fiona Nash revealed she may be a dual citizen.
Senator Nash says she has received advice from the UK Home Office that she is a British citizen.
The Senate will be asked to refer her case to the High Court when parliament resumes on September 4 but she will not step down from her portfolio responsibilities in the meantime.
Senator Nash told parliament on Thursday night she sought advice about her citizenship status on Monday from the UK Home Office following revelations the party leader and Deputy Prime Minister Barnaby Joyce was a dual citizen with New Zealand.
A caseworker advised her she was "of the view" that she was a British citizen by descent through her Scottish-born father.
The government sought legal advice from the UK, received on Thursday night and considered by cabinet, as well as advice from the solicitor-general, she said.
"I can advise honourable senators that on the basis of the solicitor-general's advice, the PM has indicated to me that he sees no reason for me to stand aside from my portfolio responsibilities.
"I will also continue as deputy leader of the National party."
Senator Nash is the sixth MP to be referred to the High Court over dual-citizenship and the third government minister, following the referral of Mr Joyce and Matt Canavan, who resigned from cabinet after discovering he was an Italian citizen.
Under the constitution, dual citizens are disqualified from sitting in parliament.
But there seems to be confusion over whether British citizenship by descent is granted automatically or must be applied for.
Senator Nash said she was born in Sydney and had very little contact with her father after her parents divorced when she was eight.
Both of her parents have since died.
"Growing up, my parents always told me that I was not a dual citizen," she said.
"My understanding since early childhood was that in order to be a dual British citizen, I would need to apply for it.
"Indeed, an internet search reveals a host of websites that say having a Scottish-born father allows one to apply for citizenship and mentions nothing about automatic citizenship by descent."
Manager of opposition business in the Senate Katy Gallagher questioned why Senator Nash made the revelations just before the Senate rose for a two-week break, given she discovered she was a dual citizen on Monday.
"Senator Nash's statement means the entire National Party leadership is now facing disqualification from the parliament," she said in a statement.
"Malcolm Turnbull needs to explain why he is holding Mr Joyce and now Senator Nash to a lesser standard than Matt Canavan and not requiring them to stand down."