Criminals are targeting Auckland's Sky City and other casinos because they see them as an easy way of laundering hundreds of thousands of dollars from crimes such as drug dealing.

Inspector Rob Abbott, area commander for Auckland central business district and liaison officer for Sky City casino, said police and the department of Internal Affairs knew Sky City casino was a target for money launderers.

"We know that certain criminals go through there and try to launder money through there," he said. Apart from that, the casino itself was a relatively crime-free area, except for "run-of-the-mill" disorder.

A Weekend Herald inquiry has identified a former Sky City staff member who was a dealer at the casino and alleged that money laundering happened "all the time" in the VIP room.

The former dealer, who did not want to be named, said Sky City was "fully aware" that money was laundered through the casino, just as it knew that loan sharks operated there.

"Over 50 per cent of VIP players are involved in criminal activity such as money laundering," said the former dealer, who worked at Sky City for a decade.

"I clearly recall this being mentioned to a group of gaming staff in a briefing to us from a senior manager."

Three high-stakes gamblers, who also did not want to be identified, said they were aware of money being laundered in New Zealand casinos.

A Sky City spokeswoman said it was difficult to respond to anonymous, unsubstantiated allegations about money laundering. The casino encouraged anyone with problems to advise the casino directly so it could act.

Stephen Lyttelton, the former acting chief executive of Christchurch Casino until he quit three weeks ago, said he raised concerns about money laundering there during a board meeting on May 31.

The South Australian state government claimed last week that Sky City's Adelaide casino was being used to "wash criminal cash" by motorcycle gangs.

Police in South Australia are to be given extra powers to issue barring orders for the Adelaide Casino that "will help curb money laundering and other criminal activity at the venue".

The claims about Christchurch casino are being investigated by the Department of Internal Affairs, and Minster Rick Barker said he was prepared to broaden the inquiry to include either Sky City or loan sharks in general if it was felt to be necessary.

Mr Barker also told the Weekend Herald he wanted Internal Affairs to "clamp down further" on money laundering in casinos.

The Green Party and Problem Gambling Foundation are calling for a public inquiry into loan sharks, money laundering and other criminal activity in casinos.