National leader Todd Muller says the magnitude of economic downturn due to Covid-19 has not yet sunk in to the public or to the media because they have been pre-occupied by the "shambles" at the border and quarantine centres.

But he says National will present a plan to the electorate before the election setting out how it will respond.

And later this month he says he will announce the largest infrastructure package in New Zealand's history.

Muller made his comments in a major speech to the Christchurch Employers' Chamber of Commerce today, in the same week his Clutha-Southland MP Hamish Walker shocked his party and the country over breaching the privacy of Covid-19 patients. Walker yesterday announced his departure from politics at the September 19 election.

Muller said National's full economic plan would not be finalised until after the Government released the Pre-Election Economic and Fiscal Update (Prefu) in August.

It would be available by September 2 when overseas voting began, to be followed by early voting, which started on September 5.

He said the plan's framework was made up of five components: responsible economic management; delivering infrastructure; reskilling and retraining the workforce; a greener, smarter future; and building stronger communities.

"National will be releasing each of these components in a series of major speeches through this month and into early August to give New Zealanders time to scrutinise each element," he said.

"With Labour not having anything to offer except 'borrow, spend and tax', National understands that responsible government is about creating a deliberate and considered plan – and then following it."

Muller said that when the earthquakes devastated Christchurch, it was a body blow to the whole country.

"The National Government took decisive action to generate the rebuild. Our legacy isn't one of ruined buildings behind fences, awaiting insurance settlements, it's of a new vibrant city, from the beautiful riverside to the shiny new buildings."

A major part of that recovery strategy was the Christchurch Central Recovery Plan, put together in just 100 days.

"Our execution of that plan returned life to a devastated CBD.

"National knows how to shape a plan that delivers. It is going to fall to us again to rebuild New Zealand from Covid-19 and the lockdown.

"The Prime Minister told her party rally over the weekend that she had no playbook or plan for her three years in Government, no plan for Covid-19 and no plan for recovery.

"National knows how to shape a plan that delivers."

He said Labour forecast net core debt would reach 53.6 per cent of GDP in 2024 under their policies.

"That's an eye-wateringly high level. We will work hard to try to keep it lower than that, which would put New Zealand in a better position to recover. But of far greater longer-term importance is that Labour projects that under its policies, but with a far stronger economic environment than we face today, net core debt will still be as high as 42 per cent by 2034.

"That means Labour intends a mere 11 per cent reduction in net core debt, over a decade. At that rate, we will not get back to the safe 20 per cent mark until perhaps the mid-2050s.

"I'm not hiding that my Government will borrow large amounts over the next three years, and in 2020/21 in particular. National will always be more disciplined in its spending than Labour. Yes, we will borrow what we need to, to support New Zealanders through the crisis – neither more nor less. But we will not just fling money around, the way the Labour Party is.

"Instead, we promise to spend it better and invest it better than Labour, in a way that does in fact improve New Zealand's productivity, economy, the overall wellbeing of every one of us, and which, in turn, makes it easier to pay the debt off."