WELLINGTON, New Zealand (AP) — Like squabbling siblings, New Zealand and Australia have close ties but also a rivalry that can sometimes turn ugly.

That tension spilled into politics on Tuesday, when Australian Foreign Minister Julie Bishop accused New Zealand's opposition Labour Party of conspiring to undermine her government, a claim New Zealand lawmakers say is "false" and "utter nonsense."

The unlikely dispute involves Barnaby Joyce, Australia's deputy prime minister. Joyce said Monday he'd been advised he was a New Zealand citizen and an Australian court was being asked to determine if he should be kicked out of parliament because Australia's constitution bans lawmakers from being dual citizens.

Bishop says Australia's opposition Labor Party used their New Zealand counterparts to raise questions about Joyce in the New Zealand parliament.