Judith Collins again urges Jacinda Ardern to reveal cannabis stance as Grant Robertson confirms he's in favour

National leader Judith Collins is again urging Labour leader Jacinda Ardern to reveal her stance on recreational cannabis as her finance man Grant Robertson confirmed he's in favour.

Ardern revealed during the Newshub Leaders Debate on Wednesday night that she had once tried cannabis, but she is continuing to push back against calls for her to say whether she will vote in favour of legalising it. 

"Whatever they decide, I'll implement," Ardern said during the debate, which Massey University Associate Professor Grant Duncan told Newshub is fair enough

"She should be left alone to make the decision; not only about how she votes but as to whether she tells us what her vote's going to be. When she's in that ballot box casting her vote, she's a private citizen," he said. 

"Honestly, I think it's not a big deal, she wants the people to decide. She doesn't want, as Prime Minister, to influence the debate."

But Collins has repeatedly sought a clarification from Ardern on whether she would support legalising cannabis because the National leader thinks Kiwis have a right to know. 

"I have noticed that there is a difference in Ms Ardern's attitude towards her wishes around supposedly influencing New Zealand voters," Collins said on Tuesday. 

"We know where she's voting on the referendum on End of Life Choice - she's voting for it. We don't know where she's voting on the sale and use of recreational cannabis. 

"She owes a duty to New Zealanders to tell them what her views are. I've made it very clear I'm voting for the End of Life Choice referendum and I'm voting against the cannabis one."

Collins doubled down Thursday, saying Ardern "shouldn't take New Zealanders for fools". 

"The thing is, people do have individual concerns about particularly moral issues, or what we would often call conscience issues, and they want to know where you stand on things," Collins told reporters in Northland. 

"I've always found that it's best just to explain why my views are where they are and most people will give you lots of points for that, actually; they'll give you credit for having a view even if it's not their view. 

"That's why with Ms Ardern, I don't know why she doesn't just say where she's going to vote on the cannabis referendum because people in my experience respect someone who has the courage of their convictions, even if they don't agree with those views."

Robertson is the latest from Ardern's caucus to confirm that he will be voting in favour of the Cannabis Legalisation and Control Bill, which if it passes in the referendum, would go back to Parliament to decide if it should become law. 

"I will be voting in favour. I'm in the camp of people that believe that the smoking of cannabis is going to happen, and it's happened for many decades in New Zealand," Robertson told Magic Talk on Thursday. 

"We're much better off having an environment where it's regulated, where we can get the health messages out and we can get the gangs - who are at the core of the supply of it - out of the way as well."

Labour's Phil Twyford also recently confirmed he will be voting in favour. 

"If we legalise it, regulate it, and tax it, we can limit access by young people, control the quality and strength of the drug, and take more of a health-based approach to people who abuse the drug," Twyford said. 

Robertson said Ardern has "made very clear right from the beginning" that her job as Prime Minister will be to implement what comes out of the referendum. 

"She doesn't think it's in the best interests of New Zealanders for her to be in there and people to take a particular message from that... If New Zealanders vote in favour of the referendum, then there will be reform," he said. 

"If New Zealanders vote against it, then there won't be... She wants to leave it to New Zealanders to direct us. That's her choice, and it's not as if she's been inconsistent about it."

The latest Newshub-Reid Research poll showed a majority of voters will vote against the legislation in the referendum.