The Turnbull government has again been plunged into a citizenship crisis, with Senate President Stephen Parry revealing he may be a dual citizen.

Only days after the High Court disqualified five parliamentarians, the Tasmanian Liberal senator on Tuesday said he believed he may hold UK citizenship. If this is confirmed by UK authorities, he will immediately resign from Parliament.

Senator Parry’s revelation comes after the High Court thrust a byelection on former deputy prime minister Barnaby Joyce, disqualifying him and four senators from Parliament under Section 44 (i) of the constitution.

As Senate President, Senator Parry, who earns $348,320 a year, oversaw the referrals of six senators to the High Court over dual citizenship.

He has contacted the British Home Office seeking confirmation of his citizenship status, he said in a statement to the Senate on Tuesday afternoon.

Barnaby Joyce is fighting a byelection in his seat of New England. Photo: AAP

Senator Parry said he did so after the High Court’s unanimous decision on Friday provided “absolute clarity” over Australian’s citizenship law.

“In the event that I am found to hold British citizenship by virtue of my father’s status, then I will clearly be in breach of Section 44 (i) of the Constitution and would therefore resign as President of the Senate,” he said.

“I would further resign as Senator for the State of Tasmania and not await the outcome of any referral to the High Court, as I believe the High Court has made it abundantly clear what action is required.”

Senator Parry’s father moved from the UK to Australia in the 1950s, leaving him vulnerable to holding citizenship by descent in a similar situation to former Nationals deputy leader Fiona Nash.

The development has already reignited calls for an audit of the eligibility of all parliamentarians, as advocated by the crossbench but rejected by the major parties, and may also bolster Mr Joyce’s proposal for a omnibus referendum that would consider a change to Section 44 of the Constitution.

On Sunday, Attorney-General George Brandis said he had “no reason … to believe that there is any other Coalition member” who held dual citizenship.

“Surely the time has come for the Libs and ALP to back the Greens’ call for an audit of all MPs and end this crisis,” Greens leader Richard Di Natale tweeted on Tuesday afternoon.

Senator Parry, who turned 57 on Tuesday, would be the first Liberal parliamentarian hit by the citizenship crisis that claimed Mr Joyce and his former Nationals deputy Fiona Nash.

Constitutional cloud looms

The news of Senator Parry’s potential disqualification comes as the Liberal politician in line to replace Ms Nash is placed under a possible constitutional cloud.

Hollie Hughes, the NSW Liberal candidate who is tipped to win the recount ordered after the High Court disqualified Ms Nash over dual citizenship, could be vulnerable to a challenge under section 44 of the constitution, experts have said.

That is because Ms Hughes, a one-time aide to the former Liberal senator Bill Heffernan, was recently appointed by Attorney-General George Brandis to the Administrative Appeals Tribunal.

Hollie Hughes (left) is in line to replace the Nationals former deputy leader Fiona Nash. Photo: AAP

Under section 44(iv) of the Constitution, members of Parliament must not hold an office of profit under the crown when they nominate for election. The law saw independent MP and former school teacher Phil Cleary booted from Parliament in the early 90s.

Constitutional law experts Anne Twomey, of the University of Sydney, and the University of New South Wales’ George Williams, have both argued Ms Hughes could face difficulties because of the precedent set by the 1992 Sykes v Cleary case.

The New Daily contacted Ms Hughes for comment.

The Greens have also found themselves facing another possible constitutional headache, with Queensland candidate Andrew Bartlett, who is in line to replace Larissa Waters, also facing questions under s44 (iv).

Mr Bartlett, a former leader of the Democrats, worked at a university while he nominated for the Senate.