The richest Kiwis are getting richer, and the growing inequality across the world has led to the rise of Donald Trump and the Brexit vote, Labour says.

New Statistics New Zealand data shows the richest 10 percent have hoarded more than half the country's wealth, with the bottom 40 percent scraping by with only 3 percent.

And the gap between rich and poor has widened in the past decade.

As of June 2015, the average household net worth was $289,000, but one in 20 households owe more than they own.

Houses make up the bulk of most families' non-financial assets, accounting for 59 percent. Mortgage debt accounts for more than 60 percent of their liabilities, however.

"Nearly three in five New Zealand households living in their own home had a mortgage, with a median mortgage value of $172,000," says Labour market and households statistics senior manager Diane Ramsay. "Overall, for every $1 of assets they have, New Zealand households have 12 cents of debt."

Labour's finance spokesman Grant Robertson says this kind of gap can make people feel left out or left behind.

"The real fear that we have is that we've seen from Brexit and from the rise of people like Donald Trump is what can happen when inequality grows. People feel excluded from society, excluded from politics and people who are peddlers of fear and hate can capitalise on that.

"So this is a problem from an economic point of view. It's a problem from a social point of view and, to my mind, the Government should be prioritising reducing inequality," he says.

But Prime Minister John Key says the Brexit and Trump examples weren't right because the figures have been roughly consistent over time.

"It's not surprising it's getting a little bit more that way because in reality -- better off New Zealanders will own assets, particularly houses, and those house prices have been rising.

"We want to see the less well-off being able to afford houses. That's one of the reasons why we run programmes like KiwiSaver and HomeStart, which allows people to get a foot on the asset ladder and for most Kiwis the asset they'll own will be a home."

Mr Key says while those at the top own more assets because of their ability to save, there are "very heavy levels" of wealth redistribution in New Zealand.

The Stats NZ figures show inequality is stark between ethnic groups:

Even accounting for the younger populations found in Pacific and Maori families, the inequality remains, says Statistics NZ.

Young people -- between 15 and 24 -- had the lowest net worth, averaging $1000. This is largely down to student loans.

Between 2003 and 2010, the top 10 percent had around 55 percent of the wealth. This has expanded to 60 percent over the past five years.

Newshub.