SYDNEY • Embattled Australian Prime Minister Malcolm Turnbull lost his grip on Parliament when another of his coalition's MPs resigned yesterday, the latest victim of a constitutional crisis over politicians who hold dual citizenship.

Former tennis star John Alexander, who represents a Sydney district for Mr Turnbull's Liberal Party, announced he was resigning after being unable to determine if he had inherited British citizenship from his immigrant father.

His resignation followed an Oct 27 ruling by Australia's High Court that forced five other politicians to quit Parliament because they had fallen afoul of a previously obscure constitutional rule that bars dual citizens from sitting in the Senate or Lower House.

The five included former deputy prime minister Barnaby Joyce, leader of the rural-based National Party, which rules in a coalition with the Liberals.

When Parliament convenes tomorrow without Mr Alexander, Mr Turnbull will control only 74 of the 150 seats in the House of Representatives, with the opposition Labor Party holding 69.

Minor parties and independents fill the remaining seats.

Labor frontbencher Tony Burke vowed yesterday to heap pressure on the government by pushing legislation opposed by Mr Turnbull's coalition but supported by independents.

"As of today, no matter which way you look at it on the floor of Parliament, this is now government without a majority.

"It's a prime minister without authority," he said.

Mr Turnbull brushed aside the likelihood of a no-confidence vote or setback on key legislation.

"There is no question of that happening," he said in Danang, Vietnam, where he was attending the Apec summit.

In announcing his resignation, Mr Alexander said the High Court ruling had forced him to examine his own citizenship status, even though he was born in Australia.

"I have always believed that I am Australian and solely Australian," he said at a press conference.

"I can no longer, with sufficient certainty, maintain the belief that I have held through my 66 years," added Mr Alexander.

He will now have to run in a by-election in Sydney's Bennelong district to return to Parliament, and that race is expected to be competitive.

Similarly, Mr Joyce needs to run for re-election in his Queensland constituency next month, though he is heavily favoured to retain his seat.

Mr Turnbull, anxious to recover his parliamentary majority, challenged Labor yesterday to come clean over its members who might hold dual citizenship, but the party has so far snubbed the idea.

AGENCE FRANCE-PRESSE