Willis would not give an ironclad commitment that she would have pruned spending to bring the books into surplus by 2024 as Treasury had originally forecast - she wants to see the full set of figures on Budget Day.
"Let's see what the figures are. I'm very conscious we don't know what the size of the deficit is. We don't know what the size of the projected debt is," Willis said.
"I would have had a look at the fact that I've got very high employment in the economy and wondered why it is that I can't get the books in balance," Willis said, describing what she would do if presented with deteriorating forecasts.
Despite not explicitly promising cuts, Willis said were she in the Finance Minister's shoes, she probably would have asked ministers to make savings.
"I would have said to my ministers, New Zealanders are doing it really tough right now. Most households are slipping a little bit backwards each week as inflation eats up their wages," Willis said.
"What are we doing across our government departments and agencies to prioritise better?" she said.
The current Government will add $6 billion worth of new day-to-day spending programmes in the forthcoming Budget (spending overall is coming down as emergency Covid spending winds up).
The previous National Government delivered two "zero" Budgets, meaning they included no additional spending. Luxon suggested the days of zero Budgets were over.
"We're going to continue to be a Government that increases Budgets around health and education," Luxon said.
"Those are the big pillars that drive prosperity and productivity," he said.
Luxon said Labour had increased Crown spending by 68 per cent while in office, evidence of a lack of fiscal discipline. Core Crown spending was just under 40 per cent in the nine years National was in office.
Robertson has done away with the Government's traditional debt target, and moved to a debt "ceiling". Instead of trying to get debt to a certain level by a certain date, Robertson has decided core Crown debt should not be allowed to rise above 30 per cent of GDP. The target means the Government cannot debt-fund additional day-to-day spending except in a crisis, but it can borrow for capital investments.
National has no position on this yet - and wants a Treasury briefing before the Finance and Expenditure Committee before it decides whether to back the new measurement or not. Labour members on that committee have blocked such a briefing.
"We want to ask Treasury more questions about that. It's frustrating we've been blocked from asking questions about that," Willis said.
Willis said Treasury's written advice said there "can be a case for a higher debt ceiling but for that to make sense for the economy you have to be absolutely sure that any investment in infrastructure meet a cost benefit analysis and have been rigorously tested".
Willis said she wanted to see what tests the Government was running on value for that spending.
As for what National might look at trimming back on, Willis and Luxon said the party would not discuss whether or not the Government's policy of free first-year tertiary study (costing $541 million this year) would go under National.
Luxon fleshed out National's position on the Government's Emissions Reduction Plan, which set a target of reducing driving by 20 per cent by 2035.
Luxon said the Government should not be setting targets for driving.
"The Government should focus on removing emissions, not micromanaging where Kiwis go and how much driving they do," he said.
National has been reluctant to support the pricing of agricultural emissions. It is currently moving from a position of outright opposition, to awaiting the outcome of the Government's He Waka Eke Noa negotiation with agricultural sector groups before taking a firm position.
Act leader David Seymour on Tuesday said eventually consumers would demand some form of emissions pricing, although he did not think there was a case for emissions pricing currently.
Luxon had some support for this.
"I've been spending a lot of time with farmers. They all acknowledge consumer behaviour is changing, trading partners are expecting it [emissions pricing], and we need to be able to continue to make progress here and the way that they have evolved their practices over 15 years to where they are today and where they need to get to.
"They know they need to change," Luxon said.
"Everyone gets the problem - we're all aligned on that. It's just the means and the fact the industry is coming up with its own solution on how to deal with methane is a good thing," he said.
