Police have taken $11.6 million worth of cash, houses, boats and motorcycles in the past eight years under the act.

They say it is hurting criminals, but admit the use of rented properties for uses such as drug-selling "tinny houses" has increased.

Detective Inspector Cam Ronald told the police magazine Ten-One: "Gangs especially and people selling drugs in city areas are using rented properties as they can't be forfeited [under the act]."

He said criminals did not necessarily escape lightly, as they faced heavy fines if it was proved they had made money from their crimes.

Me Ronald said the act was being mainly used against drug dealers, but it should be used to fight a much wider range of serious crimes.

He said the act was one of the most effective tools the police had.

"We know it's really hurting the criminals. They are stripped of their assets, and it's very hard to come back from time in prison and start building up those assets again."

Disgraced former Hong Kong prosecutor Warwick Reid paid the largest single penalty - $763,000 - imposed under the act.

He had assets worth $1 million seized after accepting a bribe of the same amount from a Chinese man.

The largest overall seizure is $1.5 million worth of property and assets taken from owners of a methamphetamine laboratory last year.

Other big hauls include a $495,000 South Canterbury farm last year, $325,000 in cash from morphine dealers in Hamilton two years ago and $110,000 cash from drug dealers in Tauranga.

Most of the money goes into the Government coffers, although mortgages on seized properties are paid.