Federal Labor MP Justine Keay has refused to reveal when the UK formally revoked her citizenship, amid questions about the validity of her election.

Key points: Justine Keay won't say when she renounced her UK citizenship or provide proof

Justine Keay won't say when she renounced her UK citizenship or provide proof Section 44 of the constitution disqualifies dual nationals from governing

Section 44 of the constitution disqualifies dual nationals from governing Two Greens senators have resigned, one Nationals senator has stood down from Cabinet over s44

The Tasmanian MP was a dual-British citizen before the 2016 election, and has not said when the renunciation was officially confirmed.

In a statement, a spokesperson for Ms Keay said: "Justine's renunciation was received by the UK Home Office before the close of nominations, and she was cleared by the party to stand."

The ABC asked Ms Keay for a copy of the declaration of renunciation, but the request was denied.

Tasmanian Liberal senator Jonathon Duniam called on Ms Keay to make the document public.

"That's all we need to see, one piece of paper, and that's what I'm asking for her to provide so we can get this issue out of the way and get on with issues that actually matter to Australians," he said.

"If she hasn't renounced her citizenship in time she does have a bit of a problem, as does the Labor party."

Sorry, this video has expired Antony Green explains Section 44i of the Constitution

Under Section 44 of the Australian Constitution which governs eligibility for Parliament, people may be disqualified from election if they have "an acknowledgment of allegiance, obedience, or adherence to a foreign power, or is a subject or a citizen or entitled to the rights or privileges of a subject or a citizen of a foreign power".

The laws recently claimed the political careers of former Greens senators Scott Ludlam and Larissa Waters, after they discovered they held dual citizenship.

Nationals Senator Matt Canavan is also facing scrutiny after learning his mother had registered him as an Italian citizen.

The former resources minister has quit Cabinet and the Government will refer the case to the High Court to decide his fate.

Ms Keay's spokesperson said the Labor Party had an extensive vetting process to ensure candidates were eligible under the constitution.

"It's a critical part of the nomination process and a candidate can't be nominated without clearing this process," they said.

Sorry, this video has expired Politicians 'have to check' their citizenship, says Barrie Cassidy

Do the laws need to change?

Meanwhile the Deputy Prime Minister Barnaby Joyce said any plans to change the Section 44 of the Constitution would fail.

He felt most Australians still believed parliamentarians should only have allegiance to one country.

"I'm honest about this. Most Australians would think oh no, I think it's fair that you should only be a citizen of one nation," he said.

"Every time you put that up, it's just a mammoth amount of work to get everybody on the same side and constitutional change is incredibly difficult.

"You're not going to get the Australian people across the line on it. It would fail."

Mr Joyce said he did not believe politicians affected by the laws were deliberately trying to mislead the public.

"For all of them, even Scott Ludlam and Larissa Waters, there's no maliciousness in this," he said.

"This is oversight."