In Opposition Labour proposed borrowing $11 billion more than National by 2021, but economists are warning borrowing could end up being billions higher than Finance Minister Grant Robertson (pictured) has proposed.

Finance Minister Grant Robertson maintains the Government still plans to cut New Zealand's debt levels, as economists warn billions more will be borrowed over the coming years.

In Opposition Labour laid out a fiscal plan which would borrow around $11 billion more than National had proposed, but still cut debt as a share of the total economic output from 24 per cent to 20 per cent by 2022.

The plan formed a major point of contention during the election campaign, as National finance spokesman Steven Joyce was widely mocked for his claim that Robertson's plan had a major "fiscal hole".

But bank economists, who monitor the likely issuance of government bonds, are warning of pressure for Treasury to borrow billions more than Labour had signalled because of new spending promises.

READ MORE:

* Minimum wage set to jump to $20 by 2021

* New Government spending will boost NZ economy, says Reserve Bank

* Election 2017: A rough guide to Labour and National's spending plans

ANZ has forecast that Labour will borrow $13 billion more than Treasury's pre-election fiscal update maintained the former Government would over the next four years, although around $3b of that would go to the NZ Super Fund. This would see net Crown debt at 23 per cent of gross domestic product, 3 percentage points higher than Labour's plan.

Outgoing ANZ chief economist Cameron Bagrie said the estimates for new spending were "conservative", including an assumption that the new $1b a year regional development fund would come entirely from existing budgets.

"[S]pending pressures are all headed one way – and a lot depends on the economy holding up."

In the days following the election Bagrie had also warned that if National had been able to form a Government, it too was likely to borrow more than planned to secure the support of NZ First.

BNZ has also indicated it expects borrowing to be stronger than Labour had flagged. Strategist Jason Wong said the half year economic and fiscal update would probably show "in the order of" an additional $2b-$3b a year in bond issuance in the coming years.

BNZ senior economist Craig Ebert said the figures were hard to determine so early in the term, but borrowing "could amount to a number of billion dollars" more than Labour had outlined.

"Some of this is taking place in a little bit of a vacuum still, because we've heard a lot of policies but it's still a little unclear which ones have been confirmed confirmed, as opposed to just strongly proposed," Ebert said.

On Wednesday ASB revised its economic forecasts in light of the new government, which saw it cut its forecast for growth to peak at 3.8 per cent in 2018, to 3.2 per cent.

However ASB chief economist Nick Tuffley now forecasts that unemployment will eventually fall to 3.9 per cent by 2021, while wage growth would gradually rise to 2.8 per cent by early 2020, on the back of both lower migration and plans to hike the minimum wage to $20 an hour by 2021.

Tuffley said based on its forecasts, and the assumption that Labour was able to stick to its spending plans, ASB was forecasting borrowing would be $1b higher than Robertson had signalled.

"Any slippage in [spending plans] will mean more debt issuance," Tuffley said.

During question time in Parliament on Tuesday, Robertson maintained that the Government was sticking to its pre-election debt plan.

"But what we're not prepared to put up with is a situation where we do not have enough affordable homes, where we have not made contributions to the [NZ] Super Fund, and where an enormous social deficit is growing," Robertson said.

"In those circumstances a slower debt repayment track is totally appropriate."

* Comments on this article have been closed.