There will be a nine-month delay in the release of parts of the inquiry report into the Havelock North water contamination crisis.

The government-appointed inquiry panel held public hearings late last year, into how more than 5,000 people became struck down by campylobacter from the town's drinking water.

The contaminated water has also been linked to three deaths.

The inquiry's report was due to be publicly released this week.

Now Attorney General Christopher Finlayson is allowing the panel an extra nine months to finalise parts of the report.

He said there are major issues involved in this event, so the panel needs ensure it gets the report right.

"At the very start of this I said to the panel of chairs that I wanted everything done to the highest standard and so if it takes more time then it takes more time."

Mr Finlayson said the panel will deliver its report into what caused the contamination by May.

He said stage two of their report into systemic issues with water supply across the country will be due in December.