New Zealand needs to get tougher on councils supplying contaminated water.

The comment's come during stage two of hearings for the Government Inquiry into the Havelock North water contamination crisis.

Five international experts unanimously agree that the government must get tougher on councils breaching drinking water standards.

Dr Colin Fricker said no enforcement action has ever been taken in this country for water contamination.

"To have a softly, softy approach is just not the way to go. It's like saying well we will have a speed limit but if you exceed it, it doesn't matter."

He said other nations would always prosecute councils for supplying contaminated water.

"Where there has been negligence the drinking water inspector will prosecute. The most common prosecution is supplying water that is unfit for human consumption."

Drinking water expert Dr Daniel Deere agreed and told the inquiry that a tougher stance on drinking water quality will greatly improve the situation in New Zealand.

"A firmer approach would upset people but in the long run it's in the interest of the community to have a firm regulator."

No council or individual has been charged over the Havelock North crisis, which struck down more than 5000 people and claimed three lives.