But Ms Sharkie, who moved to Australia from England as a one-year-old and has previously said she had made sure she renounced her dual citizenship before the 2016 election, won't be referring herself to the High Court - despite Prime Minister Malcolm Turnbull taking the unusual step of calling her directly and suggesting she may need to do so.

Mr Turnbull's suggestion was made during a broader conversation between the pair about the citizenship fiasco that has rocked the federal parliament and, so far, cost six MPs their seats.

The member for the South Australian seat of Mayo on Thursday revealed she only received a letter from the UK Home Office confirming the renunciation of her citizenship on June 29 – 20 days after nominations for the 2016 poll had closed - which could mean she was not validly elected under a strict interpretation of section 44 of the constitution.

It is not clear if the moves that Ms Sharkie took to renounce her British citizenship constitute having taken all "reasonable steps", which raises the question of her eligibility.

In the recently concluded "citizenship seven" case, the High Court stated a person was disqualified if at the time they nominated for election, they retained the status of subject or citizen of a foreign power.

However, if it was demonstrated that the "person has taken all steps that are reasonably required by the foreign law to renounce his or her citizenship and within his or her power" they are in the clear.

Some legal experts believe "reasonable steps" only applies in situations where a nation does not allow its citizenship to be renounced.

In a statement, Ms Sharkie said that during her call with Mr Turnbull, the Prime Minister asked her questions about the dates she sought to renounce her UK citizenship, which she answered.

"The Prime Minister in our conversation suggested I may have to refer myself to the High Court. I have been open throughout about my citizenship status and have supported a full audit of all members of Parliament on this issue," she said.

But after seeking legal advice and discussing the issue with party leader Nick Xenophon, Ms Sharkhie said she believed she had taken all steps required to renounce.

"I will, of course, fully and willingly comply with the declaration of citizenship process that will soon be implemented, and if that process determines my case should be referred to the High Court, I will of course respect that. However, I am confident that I have complied with Section 44 (1) of the constitution."

If Ms Sharkie was referred it would have implications for a number of MPs, including Labor's Justine Keay, Susan Lamb and Josh Wilson, and could serve as a test case if she is referred to the High Court.

Pressure would likely build on Labor to refer that trio of MPs if Ms Sharkie is referred, given the similarity of their cases.

At the same time, the Turnbull government - which has already lost its one seat majority because of the disqualification of Barnaby Joyce - would not be able to count on Ms Sharkhie's offer of supply and confidence, further shaking its hold on power.

Ms Keay has admitted her British citizenship was not formally renounced until July 11, after nominations closed, while Ms Lamb has refused to say when her renunciation formally took place.

Both MPs argue they have taken all reasonable steps to renounce their citizenship and are in the clear.

Mr Wilson is also among the growing group of MPs who did not have confirmation of their renunciation before the close of nominations.

He was born in London during a family holiday, applied to get rid of his British citizenship on May 12, 2016, the day he was endorsed as a Labor candidate. According to tracking by Australia Post, this reached Britain on May 16.

However, Mr Wilson did not receive a letter back from British authorities until June 24, 2016, after nominations had closed.

The date on which Mr Wilson's renunciation took effect may be earlier than June 24 2016, but on Thursday, the member for Fremantle was overseas and could not be reached for clarification.

Last week, Professor George Williams told Fairfax Media that "if they received a letter saying their citizenship has been renounced by the date of their nominations they are safe. If that letter has not been received by that time of nomination then questions need to be asked about whether they have taken all reasonable steps".

Professor Anne Twomey said there was "certainly reasonable doubt" about the status of the Labor pair.

It was possible, she said, the High Court could find they had taken "all reasonable steps" to renounce British citizenship and they would - if the matter was tested - be found to have been validly elected.

"But alternatively the High Court could take a strict position and say it's the date of nomination [for renouncement that needs to be met], and that's it, you are out."

NXT Senator Stirling Griff told Fairfax Media: "Bek lives and breathes her electorate. She is an outstanding local member. Locals would not want to see her go if there is an issue with the British bureaucracy working at a snail's pace".