Former National Party leader Don Brash has criticised what he believes is Prime Minister John Key's failure to handle economic reform.
"I give him a five, because it's been a stable environment, people have been fairly happy," he says. "But he hasn't really dealt with the long-term issues facing the country."
Mr Key announced his shock resignation as Prime Minister on Monday, leaving the leadership open and a legacy in question.
Mr Brash told RadioLIVE he supports MP Judith Collins to be the next PM, after she threw her hat into the ring against Bill English and Jonathan Coleman.
"I know Judith pretty well - she and John Key and I all entered Parliament on the same day," he says. "She's someone I greatly respect."
Ms Collins has encountered controversy over her dealings with dairy company Oravida and allegations she had been seeking to undermine the then-boss of the Serious Fraud Office (SFO), Adam Feeley.
However, Mr Brash believes she has integrity for the top job.
"To suggest that she doesn't have integrity is flying in the face of facts," he says. "She's highly intelligent, she's been a lawyer in a previous career, and I don't doubt she has the integrity and the intelligence."
He says Ms Collins is more likely to attempt to deal with the difficult issues facing New Zealand.
"I think she would try and deal with some of the issues that John Key quite frankly has not in the last eight years," he says.
"Starting off for example with housing affordability, which is a major challenge for the country. It was a challenge when John Key became Prime Minister in 2008, it's even more of a challenge now of course."
Mr Brash dismisses Mr Key's pragmatic and polling-driven approach to reform.
"He hasn't done very much that Helen Clark wouldn't have done," he says. "He hasn't dealt with the very slow productivity growth in New Zealand."