Labor is demanding Deputy Prime Minister Barnaby Joyce stand aside and not vote until his eligibility to be in Parliament has been decided by the High Court.

Key points: Barnaby Joyce may be a NZ citizen because his father was born there

Barnaby Joyce may be a NZ citizen because his father was born there He's asked the High Court to rule on his eligibility for Parliament

He's asked the High Court to rule on his eligibility for Parliament He will remain Deputy Prime Minister

Parliament has referred Mr Joyce's case to the High Court to decide if he holds New Zealand citizenship because his father was born in New Zealand.

Earlier today Mr Joyce said the New Zealand High Commission contacted him last Thursday to say he might be a New Zealand citizen by descent.

He said he was "shocked" to hear the news.

"I have always been an Australian citizen," he said.

The National Party leader was born in Tamworth in New South Wales in 1967.

He said his father was born in New Zealand but moved to Australia in 1947 "as a British subject — in fact we were all British subjects at that time".

"Neither my parents nor I have ever applied to register me as a New Zealand citizen, the New Zealand Government has no register recognising me as an New Zealand citizen," Mr Joyce told Parliament.

Manager of Government Business Christopher Pyne said the Government remained absolutely confident that the Deputy Prime Minister was not disqualified under section 44 of the constitution.

"Because we are so confident of the Deputy Prime Minister's status he will continue fully, as the Member for New England, participating in the House, and he will continue as the Deputy Prime Minister and as the Minister for and Agriculture and Water Resources," Mr Pyne said.

Labor says majority Government in doubt

Manager of Opposition business Tony Burke seized on the fact the Coalition only has a one-seat majority to argue that the High Court case would determine whether the Government is legitimate.

"As of today the majority Government is in question," Mr Burke said.

He contrasted Mr Joyce's case with that of his Nationals colleague Matt Canavan, who quit Cabinet when he discovered he had Italian citizenship.

"How can he be the Deputy Prime Minister, when the standard was set by the former minister for resources that you should stand aside if there is uncertainty?" Mr Burke said.

"If there is not uncertainty, why on Earth are we referring the matter to the High Court?

"How on Earth can this Parliament be claiming to have a majority Government relying on the vote of someone who they don't know whether or not he has been lawfully elected?

"The Deputy Prime Minister should stand aside and he should not exercise a vote in this House until the matter is resolved by the High Court."

High Court to rule on several cases

Last week the Senate referred four cases to the High Court to decide on eligibility.

Mr Canavan and One Nation Senator Malcolm Roberts will both argue in the High Court that they should not be disqualified as dual citizens.

Two Greens senators — Scott Ludlam and Larissa Waters — have both quit after conceding they are dual citizens.

The High Court will make a ruling about the process for replacing the two Greens.

The court has asked people to make submissions by next Monday setting out their reasons for being granted leave to appear.

There will be a directions hearing for the four cases on Thursday, August 24.

PM urges Shorten to make sure his house is in order

Prime Minister Malcolm Turnbull meanwhile suggested Opposition leader Bill Shorten refer any Labor MPs or senators to the High Court so they can be decided at the same time as Mr Joyce and the other cases.

Mr Turnbull said it was manifestly in the national interest to have the High Court clarify what section 44 of the constitution means for a person's eligibility for parliament.

"With around half of all Australians having a foreign-born parent and with many foreign nations having citizenship laws which confer citizenship by descent, regardless of place of birth, the potential for many, possibly millions of Australians unknowingly having dual citizenship is considerable," he wrote to Mr Shorten.

"The Australian people must have confidence in our political system and resolving any uncertainty is vital."

Mr Shorten has not yet responded to Mr Turnbull's letter.