By RNZ

New Zealand's richest man, Graeme Hart, made $3.4 billion during the Covid-19 pandemic, reinforcing the urgent need for a wealth tax to help fix inequality, an Oxfam manager says.

Hart's added wealth is revealed in a new Oxfam report which is part of wider research tracking global wealth.

The report concludes that a rigged economic system is enabling the super rich to grow their fortunes amidst the worst recession since the Great Depression of the 1930s.

Oxfam New Zealand communications and advocacy director Joanna Spratt told Morning Report such wealth accumulation highlighted the urgent need for a focus on wealth tax in New Zealand.

There needed to be a living wage for everyone, more funding for healthcare and education and, crucially, proper taxation of wealth, she said.

"It's a way for government to get more revenue to make sure it invests in all people."

While Prime Minister Jacinda Ardern has taken a capital gains tax off the table under her leadership, there still needed to be engagement on the wider issue, Spratt said.

"I have noticed that people are starting to raise the issue of capital gains tax but also wealth taxes and the Green Party policy was a really good conversation starter.

"I don't think just because one individual [the Prime Minister], albeit how powerful she is, has said it's not going to happen on my watch that the rest of the population in New Zealand shouldn't be talking about this.

"We can raise the issue and keep highlighting what a powerful lever our tax system is to help get the country we all want to see, which is one where everybody lives in dignity, has a basic level of wellbeing and we have a healthy planet."

Hart's wealth gain would pay the entire grocery bill for more than 200,000 households for a year, Spratt said.

"So they're big numbers and it is surprising. But at the same this is a problem that Oxfam has been talking about for many years... Economic inequality within countries and across the world has been an issue for a very long time."

Spratt said Hart had made "strategic business decisions" during the pandemic but he was typical of a small handful of business entrepreneurs amassing vast fortunes that they did not need.

"Meanwhile, we have people across the world, the vast majority of the world's population, who struggle to get by. They're losing their jobs, they live on poverty wages and they don't get decent healthcare and education, so this tells us that there is something really wrong here with our economy."

The economic system is rigged, she said, because governments are not operating economies that work for everyone - they just aid "the fortunate few".

Many people could not earn a living wage, they didn't enjoy labour rights, and three-quarters of the world's workers could not access sick pay or unemployment benefits, so had nothing to fall back on.

"The vast majority of the world's population actually don't have an economy that works for them while there's a small number of people who just keep concentrating wealth."