Shadow minister Katy Gallagher was British when she nominated for 2016 election

Labor frontbencher Katy Gallagher can expect to be referred to the High Court after the release of senators’ citizenship declarations on Monday confirmed the ACT senator was a British citizen when she nominated for the 2016 election.

But she says she will not refer herself to the court because her legal advice was that she had taken all the steps required of her before she nominated – even though her renunciation of foreign citizenship wasn’t registered until later.

The declarations of all senators were posted online on Monday. House of Representatives MPs must produce their declarations by Tuesday morning; these will be made public within a day or so.

Gallagher, who entered the Senate via a casual vacancy during the previous term, is one of several Labor MPs likely to be referred to the court, as the citizenship crisis turns on the opposition.

The government has indicated it will refer Labor MPs who had not had their renunciations confirmed by nomination day. In these cases, the MPs took steps to renounce foreign citizenship and will argue they did all that was required.

Others likely to be referred are Justine Keay, who holds the Tasmanian seat of Braddon, and Josh Wilson, the member for Fremantle in Western Australia.

Susan Lamb, the member for Longman in Queensland, has also been targeted by the government, although her case is more complicated. She has said the British Home Office questioned whether she held citizenship to renounce, and asked for more paperwork which she could not supply.

The government says Labor should refer any of its own people whose status is in doubt. Labor has attacked the threat to refer Labor MPs but it is not disclosing what position it will ultimately take.

Sydney University constitutional expert Anne Twomey says Labor will need the court to take a liberal rather than a strict legal interpretation of the Constitution if it is to avoid byelections in its seats.

She said the ALP would have a “reasonable case” to argue in the court. But it was hard to predict how the decisions would go because there had been mixed messages.

In the 1992 Sykes v. Cleary case the court had indicated a nominee only had to take the reasonable steps within their power to renounce their dual citizenship.

But in remarks the court had made in one of the recent cases, its reference to reasonable steps was in the context of circumstances where the other country would not acknowledge renunciation. It was unclear whether this was because the court was now taking a stricter view of the test or whether it would uphold the authority of the Cleary case, Twomey said.

She said the court might also take a different view where a candidate had purposely delayed initiating action to renounce, from a case where they had been chosen late in the piece and then acted with all speed.

Keay has admitted waiting some time after she was advised by the Labor party to divest herself of her British citizenship. She has said: “I delayed it – it’s one of those things with the citizenship I knew I could never get it back”.

She told the Burnie Advocate: “If I didn’t get elected I can’t get my citizenship back and for me, it was a very personal thing”, saying it was the last tangible connection with her father.

On the other hand Wilson – who replaced another candidate at the last minute – was only endorsed by his party on May 12, 2016, for the July 2 election, and completed the renunciation paperwork the same day.

Early in the citizenship crisis Bill Shorten repeatedly declared publicly the opposition was confident that none of its MPs would be vulnerable, saying it had a comprehensive vetting process. More recently Labor has become nervous.

Shorten’s concern was clear to Malcolm Turnbull when they met some weeks ago about the citizenship crisis, which has now claimed victims across the political spectrum – although so far no Labor MPs.

The Nick Xenophon Team’s sole lower house member, Rebekha Sharkie, who holds Mayo in South Australia, is also facing referral. She too did not get her renunciation formalised before nomination.

It is not known whether there are further lower house MPs with possible dual citizenship at the time of nomination. Turnbull said at the weekend he was confident there were not any more Coalition MPs who had been dual citizens.

The declarations of senators indicated that several had been dual citizens in the last parliament before getting their affairs in order for the election.