UPDATED 1.45PM: Money laundering is a factor in the property boom, according to police research uncovered by today's Weekend Herald.

Police have concluded lawyers, accountants and real estate agents are increasingly being used to launder around $1.6 billion a year.

The information has only been released after pressure from the paper, involving an approach to the Ombudsman.

The police looked at cases involving money being seized as the proceeds of crime.

In more than half of them, a legal loophole allowed criminals to use property deals to cover up the original source of dirty money.

Furthermore, it's emerged the Justice Minister rejected advice from officials that would have closed a loophole used by money launderers.

The Weekend Herald has found Amy Adams decided instead to scope the scale of reforms it would need.

The paper said police raised concerns more than a year ago about the policy that has allowed the money laundering.

"I wanted to move quickly, but quickly bearing in mind this is not an area you want to get wrong," Adams told the Herald.

Labour's Andrew Little said the Government is dragging the chain on the issue.

He wants to know why the Justice Minister hasn't taken steps to close the money-laundering loophole in the law.

Leaving lawyers, accountants and real estate agents out of the money laundering legislation only creates questions, he said.   

"It may well be that some of these sectors, the real estate industry for example, are big donors to the National Party, and they don't want to upset them. I don't think that can be ruled out."

NZ Herald