The Cook Islands government says it is yet to decide how to disinfect the water supply in Rarotonga.
This comes as the island prepares for the completion of a multimillion dollar upgrade of its water reticulation system.
The opposition Democratic Party's Selina Napa has accused the government of duplicity, saying it has already reached a decision to use chlorination.
But the Deputy Prime Minister, Mark Brown, said that was not so.
While chlorination is used by all modern countries, including Australia and New Zealand, the government is yet to receive a report from officials, who have been consulting the community.
"The other options that are being considered are treatment of water through ozone, treatment of water through ultraviolet and also another substance that has been promoted called an analyte, which we have been advised is basically another form of chlorination," Mr Brown said.
"So there are a number of options that our officials have been asked to get more information on before providing a report to us on what they recommend."
Meanwhile, a group called Te Vai Ora Māori - The Māori Water of Life - said it was dedicated to keeping the Rarotonga water supply chemical free.
Chair Anna Rasmussen said the group comprised of Aronga Mana (landowners and residents) believed the government should not be considering chlorination.
"We chose the name Te Vai Ora Māori because it expresses the overall traditional belief that our water supply here on Rarotonga is exactly that - the water of life of the Māori of our country," Ms Rasmussen said.
"We believe that to tamper with our water supply by adding chemicals to it will have far reaching, long-term, negative repercussions on the health of our people and our environment," she said.
"This is a huge risk that we are not prepared to allow."