The Canterbury District Health Board says communities could be at risk from contaminated drinking water if changes to the way local authorities manage water supplies are approved.
Part of the Local Government Act Amendment Bill seeks to remove barriers to the development of water infrastructure and give councils more options for providing and managing water supplies.
Canterbury's Medical Officer of Health, Dr Alistair Humphrey, says the changes mirror those made by the Government of Ontario, which a judge found contributed to the deaths of seven people.
The seven died in the small Canadian town of Walkerton a decade ago after drinking E-coli-contaminated water from a bore that had been poorly monitored as a consequence of a decision to cut red tape.
In its submission on the bill the board says similar risks could develop here if the measures become law. Other health boards have raised similar concerns.
Labour MP shares board's fears
Dr Humphrey told Radio New Zealand's Checkpoint that while the current system is not fail-proof, changing the law would take away the legal requirement for councils to make proper check and balances - and that, he says, could lead to very serious health risks for those drinking the water.
Dr Humphrey says that if the proposals are approved, water supplies will be tested less often and health professionals will no longer be involved in ensuring their safety.
Labour's water spokesperson, Brendon Burns, shares the DHB's fears. He says it's unacceptable that one in five or six New Zealanders is drinking water that is either unsafe by World Health Organisation standards or not tested to determine if it is safe.