More politicians may soon be facing an identity crisis, with the British Home office confirming children born overseas to British-born parents are automatically citizens by descent.
The Home Office told AAP on Friday that since 1983 children born overseas to British-born mothers or fathers are British by descent.
Prior to 1983 citizenship by descent was passed only through the father. Children born in the UK prior to 1983 are also British, regardless of whether their parents were British-born or not.
British citizenship must be formally renounced, the Home Office said.
Under the Australian constitution dual citizens are not allowed to stand for parliament, but automatic foreign citizenship has caught several federal politicians unawares.
Seven MPs and senators, including Deputy Prime Minister Barnaby Joyce, have already been referred to the High Court to determine whether they are disqualified under section 44 of the constitution, which bans dual nationals.
A September 2015 Home Office document which details citizenship for children born outside the UK reads: “A child born outside the United Kingdom will be a British citizen by descent if either parent is a British citizen otherwise than by descent at the time of the birth”.
Mr Joyce announced his Kiwi status, passed down from his father, on Monday.
Later in the week deputy Nationals leader and cabinet minister Fiona Nash referred herself to the courts, because of dual citizenship through her Scottish-born father.
The citizenship crisis in parliament began in July when Greens senators Scott Ludlam and Larissa Waters resigned from parliament after revealing they held New Zealand and Canadian dual citizenship respectively.
Resources minister Matt Canavan resigned a week later after his mother alerted him to his Italian nationality.
One Nation senator Malcolm Roberts was also referred to the courts over the timing of him being elected and formally renouncing his British citizenship.
Senator Nick Xenophon is also in touch with the British Home Office concerning his citizenship, because Cyprus, where his father was from, was under British occupation.
Before he was first elected in 2007, he wrote to the Greek embassy and Cypriot high commission to renounce any possible citizenship.