National MP Chris Penk's been dumped from Cabinet and his ministerial portfolios, after instigating today's failed coup. 

Prime Minister Chris Luxon managed to fight off the challenge for his leadership - at a three-hour caucus meeting in Wellington today. 

He says Penk's role is now untenable. 

NZ Herald political editor Thomas Coughlan says Penk was likely running the numbers - for Erica Stanford or Chris Bishop to contest the leadership. 

"I think there was a classic stalking horse or sometimes they're called kamikazes - they launched the attacks and destabilised...so that it triggered the confidence vote." 

Paul Goldsmith will pick up the Defence, Veterans, Space, GCSB, and NZSIS portfolios. 

Simon Watts will become Minister for Building and Construction.

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