The National Party is continuing to push for the release of emails from former Cabinet minister Clare Curran's private account.
National Party leader Simon Bridges believes there could be information in the emails which forced Ms Curran's resignation.
"We could be quite cynical about a pre-emptive resignation here," he told Morning Report.
"Let us see the Gmails, let us see the official information.
"This is a government that said they would be the most open and transparent ever - let's see the proof in the pudding."
Ms Curran was demoted from Cabinet and stripped of two of her portfolios last month after she failed to properly declare a meeting for the second time.Ms Curran resigned on Friday, two days after she struggled to answer questions in Parliament on what government business she conducted via her personal email account.
"There are serious questions to answer" - Simon Bridges
Mr Bridges also criticised how the Prime Minister was dealing with sidelined Customs Minister Meka Whaitiri, who has been accused of "manhandling" her new ministerial press secretary.
The prime minister needed to look her in the eye and ask her the questions, he said.
However, he said that his own inquiry into who leaked details of his travel expenses to media was different.
"If you look at the Meka Whaitiri situation, actually that's a step up, because what we are talking about there is not actually a backbench member of Parliament's relationship with the leader of the opposition, it is a minister of the Crown's and the confidence that the prime minister has in him or her."
All National MPs had signed a waiver to disclose "effectively all digital communication that could be in relation to the leak and the anonymous text only", he said.
"The reality is, I don't know. I don't know if it's a National MP, I don't know if it's a National staffer but I certainly can't rule out that it is wider than that."
Māori language week
Mr Bridges said National had done a number of videos to celebrate Māori language week and he was "really pleased" to see Nikki Kaye's law to make learning a second language compulsory in primary and intermediate schools go into parliamentary systems.
"I don't support compulsory," he said when asked about bringing more te reo into schools.
"I think in an area such as this it is much more motivating if children choose it for themselves."