Winston Peters had a fiery clash with Paula Bennett in Parliament on Thursday, accusing her of asking "mindless questions" and diving into a "moronic abyss".
Their confrontation came during Question Time, after the deputy leader of the Opposition challenged the Deputy Prime Minister, who was answering for Prime Minister Jacinda Ardern, over the Employment Relations Amendment Bill.
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The legislation would end the 90-day trial period for big business and would enforce multi-employer collective agreements. Mr Peters has faced questions over whether New Zealand First will support it, with unions fearing the employment law reforms could be hijacked by Mr Peters.
New Zealand First gave the legislation its support at Cabinet, which means it should back it through to law - but Mr Peters has since been cagey, describing the legislation as a "work in progress".
"Can she confirm that the Labour-led Government unanimously voted for the Bill at select committee and the Bill has now been prepared for a second reading, and do they know how they will vote for it?" Ms Bennett asked Mr Peters.
But Mr Peters had a scathing reply.
"On behalf of the Prime Minister, if that member will not conform to the proper language of an MMP environment we do not intend to answer her mindless questions," he answered.
"She knows full well the construction - we can handle it, and that's why we're here and that's why they're over there, because they just don't grasp what the new environment looks like."
Implying Mr Peters was the real leader of the Coalition, Ms Bennett continued her dogged questioning, asking if the Government supported the Bill as it's currently written.
Mr Peters was quick to fire back.
"Look, we're not going to have a dive to the moronic abyss that the member wants to go to," he retorted.
"We are talking about a process of the full committee of the House and then onto the third reading - that's what's being targeted, that's what we'll do."