Dual citizen Kakoschke-Moore quits Senate

South Australian senator Skye Kakoschke-Moore has resigned from parliament after revealing she is a dual citizen having inherited British citizenship from her mother.

The Nick Xenophon Team senator, who was born in Darwin in 1985, revealed her mother was born in the former British colony of Singapore in 1957.

"I am heartbroken by this news," she told reporters in Adelaide on Wednesday.

Senator Kakoschke-Moore believed for her entire life she was not eligible because usually where a parent is born outside of the UK they are unable to pass their citizenship on to their children also born outside Britain.

Her father had even made inquiries when the family lived in Oman when she was 12 for getting her a British passport but she was told she was not eligible.

The senator said she received "extremely surprising" advice from the Home Office last Friday, which she got confirmed by a UK-based barrister on Tuesday night.

Her mother obtained British citizenship when she was born in Singapore and retained it when Singapore got independence in 1963 because her father was born in the UK.

She went on to obtain right of abode in the UK under a 1971 law and when the British Nationality Act 1981 was enacted her mother effectively became a citizen otherwise than by descent.

"She was therefore able to pass her citizenship on to any children born outside of the UK," Senator Kakoschke-Moore said. "I am therefore a British citizen."

She will refer her case to the High Court but says she still has ambitions for returning to the Senate.

"My time as a senator has been the most fulfilling of my life," she said.

"This party is my passion, serving the people of South Australia is my passion. I have unfinished business as far as I'm concerned."

Party leader Nick Xenophon was devastated by the news, thanking the senator for her outstanding work.

"She's been a class act in the Senate," he said.