Prime Minister Jacinda Ardern has let NZ First leader and Deputy Prime Minister Winston Peters off the hook for admitting – then denying – having secret photos of journalists taken.

Speaking to media this morning, Ardern was at pains to put distance between herself and Peters over the issue, repeatedly pointing out that the photos were a matter for New Zealand First, not the Government.

"It would simply not be the expectation of taxpayers' that I manage three parties as well as the Government," she told Newstalk ZB.

Photos of RNZ and Stuff reporters, who had been investigating the mysterious NZ First Foundation, appeared on a Whale Oil-linked blog last week.

Peters had initially said "we" had taken the photos to show the kind of "behaviour" going on.

He later backtracked and said it was simply a "supporter" who took the photos.

But how they ended up on the blog remains unclear.

Ardern this morning failed to condemn Peters' actions in the saga, fending off questions by saying it was a "matter for New Zealand First".

"I am in charge of the Government. I do not take the personal responsibility for the conduct of the various political parties – that would just be an overstep," she told ZB.

She said Peters was accountable to her only in his capacity as a Minister – Peters is Minister of Foreign Affairs, and Deputy Prime Minister.

Speaking to RNZ, she continued to distance Peters' actions, as NZ First Leader, from his duties as a Cabinet minister.

"I'm the Prime Minister. I do not run three separate political parties. I don't think it's unfair or unreasonable to say these are matters for NZ First – it's not for me."

Asked if Peters was upholding the highest ethical standards, as outlined in the Cabinet manual – the rule book for Ministers – Ardern wouldn't directly comment.

According to that manual: "At all times, ministers are expected to act lawfully and to behave in a way that upholds, and is seen to uphold, the highest ethical standards".

"This includes exercising a professional approach and good judgment in their interactions with the public and officials, and in all their communications, personal and professional."

Ardern, however, again pointed out that Peters had done nothing wrong in his capacity as a Minister.

"I don't see these as things being explicit to the Cabinet manual which is the conduct of how we run the Government.

"This is not relevant to the role he plays as Minister of Foreign Affairs."

She confirmed that Peters was safe in his portfolios.