Sydney, Australia - The prime minister has postponed a trip to Israel in order to deal with a constitutional crisis after the High Court ruled five members of parliament - including the deputy prime minister - should never have been elected because they're dual citizens.

Deputy Prime Minister Barnaby Joyce was a member of parliament in the House of Representatives where Australia's government had a majority of just one, which it lost on Friday.

"I had no reason to believe I was a citizen of any other country but Australia. I was born just there," Joyce told reporters, pointing to an area in the city of Tamworth. "You take the hits and you take the sacrifices … I'm not going to cry in my beer and I'm going to get back to work."

Having renounced his New Zealand citizenship, Joyce will now stand in a by-election on December 2 in the constituency he thought he already represented.

Joyce's ineligibility also raises questions about the decisions he made as a minister.

Constitutional lawyer Anne Twomey said there may be a legal challenge to any decision Joyce took once questions had been raised about his eligibility.

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"It might well be that those decisions are vulnerable," Twomey told Al Jazeera.

Australia's constitution bars anyone from standing for parliament who "is a subject or a citizen or entitled to the rights or privileges of a subject or citizen of a foreign power".

Most of the disqualified MPs were considered born to Australian parents abroad, or had been born in Australia to a foreign parent.

All except one said they did not know they were dual citizens when they stood for parliament. But the High Court judges ruled ignorance was not an excuse in law.

Prime Minister Malcolm Turnbull was due to travel to Israel on Saturday. By convention his deputy would have taken over his responsibilities during his absence.

But after the court decision, a spokesperon for the prime minister told Al Jazeera his Israel trip has been put on hold.

The four disqualified senators will now be replaced in parliament by other members of their parties.