SOUTH Australian senator Skye Kakoschke-Moore has resigned from the Australian Parliament after she was confirmed as a British dual citizen by descent.
Ms Kakoschke-Moore becomes the third Nick Xenophon Team politician to be caught up in the citizenship crisis gripping Federal Parliament.
Her mother was born to British parents in Singapore in 1957 before she moved to Australia in 1970 - which made Ms Kakoschke-Moore eligible for a British citizenship.
She will quit the Australian Senate immediately, and will be referred to the High Court.
Ms Kakoschke-Moore choked back tears as she said she had decided to quit after receiving legal advice on Tuesday night.
"Based on this advice, I am resigning from the Senate today and will be requesting that my matter be referred to the High Court when the Senate sits next week,'' she said.
"My time as a senator has been the most fulfilling of my life. I am proud to say that when I reflect on my first speech, many of the goals I set for myself and those which I couldn't imagine that the time have already been achieved.''
Ms Kakoschke-Moore said she had believed she was ineligible to be a British citizen but had approached the British Home Office last week for information as part of the new requirement for senators to table information about their citizenship status.
The Home Office advised her on October 17 that she could be British and a barrister provided confirmation on Tuesday night.
NXT and SA Best leader Nick Xenophon said he hoped that Ms Kakoschke-Moore would run for the Senate again at the next federal election.
"I'm devastated by the news, all my colleagues are devastated by the news,'' Mr Xenophon said.
"Skye Kakoschke-Moore has done outstanding work and this is not the end of her political career, I think it's the end of a chapter of her political career."
Mr Xenophon said it was unclear how the Senate vacancy would filled.
If the High Court orders a recount of ballot paper, former NXT candidate Tim Storer - who has since quit the party - could win the position.
Former senator Mr Xenophon was referred to the High Court because he held a UK overseas citizenship but was ruled to be eligible.
Ms Kakoschke-Moore said she was proud to have fought for a permanent compensation scheme for defence abuse victims and for "Carly's law" to protect young people from online predators.
Ms Kakoschke-Moore was born in Darwin in 1985 before moving to Oman with her family when she was nine where she lived for 10 years.
She moved to Adelaide in 2005 to study at Flinders University.