Australian Justice Minister Michael Keenan has denied he is a British dual citizen, after becoming the latest figure caught up in a political saga.
Australian MPs and senators are not allowed to hold dual citizenship.
Five other Australian politicians are due to have their eligibility for office tested in court over claims they are dual citizens.
Mr Keenan said he renounced his British citizenship in 2004 before entering parliament.
"I am an Australian citizen and I do not hold citizenship of any other country," he tweeted.
Fairfax Media reported it took Mr Keenan two days to confirm he had renounced his citizenship. Mr Keenan accused the outlet of a "cheap grab for a headline".
He did not release documents showing his citizenship renunciation.
However, Immigration Minister Peter Dutton said Mr Keenan had "dealt with that matter" through his statements.
Mr Keenan was born in Australia but inherited British citizenship from his Durham-born father.
Like Mr Joyce, Mr Keenan sits in the lower House of Representatives, where Prime Minister Malcolm Turnbull's government has only a one-seat majority.
If any members of the government were to be ruled ineligible, it would trigger a complex process that could threaten Mr Turnbull's hold on power.
A section of Australia's constitution prohibiting dual citizens from holding office will be tested in the nation's High Court next week.