John Alexander has nine days to receive confirmation he is no longer a UK citizen or risk disqualification, according to the government’s  own reading of the constitution.

The Turnbull government has cited legal advice from former solicitor-general David Bennett QC to argue Labor MPs Justine Keay and Susan Lamb and NXT MP Rebekha Sharkie should be referred to the High Court.

The government says the politicians were ineligible for election because the UK Home Office had not confirmed their renunciation of British citizenship by last year’s June 9 nomination deadline.

Mr Alexander has until November 23, when nominations for his former seat of Bennelong close, to receive similar confirmation.

If not, he would face whatever fate awaits Ms Keay, Ms Lamb and Ms Sharkie, constitutional law experts told The New Daily. 

Mr Alexander told reporters on Monday he hoped to hear back from the UK Home Office “within a week”.

He was unaware the election date of December 16 – and thus the nomination date – had already been announced hours earlier. Journalists informed him at the press conference.

Mr Alexander told 2GB radio that same day that he had “completed the papers … and my renunciation will be verified and completed”.

“I can’t, and should not, be seeking the preselection or commencing campaigning, that is certain,” he said.

John Alexander’s citizenship status has created a fresh headache for the PM. Photo: AAP

He added: “I’ve been in contact with the High Commissioner and filled out those forms to renounce citizenship and that process happens within a few days.”

University of Sydney constitutional law expert Professor Anne Twomey told The New Daily she assumed that “given the circumstances the British government would expedite his application”.

Professor Twomey noted former Nationals deputy leader Fiona Nash’s renunciation was processed within three days of completion of her renunciation.

Liberal sources were also confident Mr Alexander would receive confirmation in time.

On Monday, the government again threatened to refer Ms Keay and Ms Lamb to the High Court if Labor did not do so, with Senate leader George Brandis arguing those MPs had a “moral obligation” to resign or face the court.

Labor has released legal advice that states Ms Keay is in the clear because she took “all reasonable steps” to renounce.

The advice, from Melbourne QC Peter Hanks, argues that the question is “not whether the foreign power has eventually got around to recording or reacting to those steps”.

Labor is yet to select a candidate for Bennelong, which is one of the country’s most diverse electorates with only 48.3 per cent of residents born in Australia.

The Liberals are confident Mr Alexander, a former tennis star and popular local member, will hold onto his seat as a result of a strong personal vote. He holds the seat by 9.72 per cent.