Over the past month, the government has been struggling with disagreements over issues and troubled ministers.
"It is with acute embarrassment we are back here," said Richard Griffin.
After Simon Bridges took out the latest leadership contest, we look back at what happened at National's last contest - when Jim McLay took over from Robert Muldoon in 1984, following the party's election defeat.
New Zealand's Prime Minister is on an official visit to Australia.
Associate Agriculture minister Meka Whaitiri has asked officials to see how animal welfare at rodeos can be improved.