Deputy Prime Minister Barnaby Joyce has told parliament he may be a citizen of New Zealand.
The New Zealand High Commission contacted the Nationals leader on Thursday afternoon to advise he may be a citizen by descent.
Mr Joyce said he was shocked to receive that information, adding he had been born in Tamworth and had always been an Australian citizen.
Mr Joyce said the federal government, based on legal advice from the Solicitor-General, is of the firm view he is not in breach of section 44 of the constitution – which bars dual citizens from sitting in parliament.
Mr Joyce, however, has asked the government to refer the matter to the High Court.
If Mr Joyce is found to be ineligible, the government – which holds a one-seat majority in the lower house – would be forced into a by-election.