National has taken the Prime Minister up on her offer to have a "re-think" of its support of a bill allowing the Commerce Commission to investigate petrol companies.
This is despite the party voting against the legislation at its first reading.
National's Commerce and Consumer Affairs Spokesman Brett Hudson said National will support the bill, but wants the Government to "axe its fuel taxes that are hurting Kiwis".
"The Government has made clear that it will require the Commerce Commission to make its first market study into fuel. We've never opposed ministerial-initiated market studies, having developed much of what this bill contains, but we do object to studies initiated by the regulator without ministerial oversight."
Ardern said she "welcomed" National's support of the bill.
"There are a number of questions that remain unanswered that we need to be looking into on behalf of New Zealanders."
National did not tell Ardern's office it would be supporting the second reading, but Ardern said she would not have expected them to.
Asked if she expected National to ask for concessions in the bill, she said the bill is in "good nick – it's just ready to be voted on."
Ardern yesterday said if National thinks the almost 40c a litre increase in fuel prices in the last year warrants an investigation – "[National] needs to support this bill in its second reading".
When law, the amendment will give the Commerce Commission the power to conduct market studies into certain sectors to gain a better understanding of how the market is functioning.
Ardern said she will be nominating the petrol companies as the first industry to be investigated.
Last week, Ardern announced the Government will be rushing the bill through the House.
She expected the bill will pass next week, regardless of whether or not it has the support of National.
But she said if the bill gets cross-party support, "it will send a very strong message that we're serious about these issues in New Zealand".
ACT Leader David Seymour, however, is not supportive of the legislation.
"It is extraordinary that the [Commerce] Commission will now be able to unleash itself on an industry without a specific allegation to respond to."