Dunedin Mayor Aaron Hawkins says public health authorities "weren't sufficiently concerned" about toxic levels of lead in drinking water until earlier this week.
On Tuesday, the council issued a notice to residents of Waikouaiti and Karitane to not drink their tap water after lead was found almost 40 times above the acceptable limit.
The Dunedin City Council wrongly stated the lead levels initially, saying the levels were four times the acceptable levels.
Hawkins then learnt on RNZ Checkpoint on Thursday it was 40 times the acceptable level.
"No I did not know that," Hawkins told Checkpoint.
"That's not ideal from an internal communication point of view."
The water is still safe to use for bathing, washing hands and clothes, however; boiling the water to drink does not remove the lead, and can instead increase its concentration.
Hawkins told the AM Show on Friday although the test showing elevated lead levels was first received in August last year, there was a systemic issue within the public health authorities.
The first test was received on August 13, 2020, however, after consultation and subsequent testing, the council determined this was a "one-off spike", RNZ reported.
During the next 14 weeks, lead was tested well below the acceptable limits, except for another high result in October.
The next high result of the lead was taken from samples in December.
"The sample in question was taken on the 8th December, we were testing for corrosivity in the water - it wasn't a drinking water test," he said.
"It came back 10 days later to someone who was on leave and it went to an unmanned inbox. That was opened in January when that staff member returned from leave."
"This is a systemic issue and that has since been addressed."
Hawkins says the test results were sent to public health authorities and the advice received was to "keep an eye on things" and "come back and see them in three weeks".
Hawkins says issuing a 'do not drink' notice has been done as a precautionary measure - but he wouldn't offer his advice on health concerns.
Asked by The AM Show host Duncan Garner how dangerous the situation is and what his health concerns were for the community, Hawkins said: "I'm not a medical doctor so I'm not going to offer a view on health concerns. Those are questions best put to Public Health South"
"They [Public Health South] are quite clear that the 'do not drink notice' has been done as a precautionary measure to give us time to try and find the source of the contamination and fix the problem, but I also know that this is definitely a distressing and destructive thing to happen to a community."
Public Health South told RNZ in a statement: "We had not advised that the community should be notified in relation to the high result in August as the normal pathway for a one-off exceedance is to undertake further testing."
However, it remained unclear whether Public Health South explicitly advised against telling the public as further calls went unanswered.
The Ministry of Health said on Thursday blood tests for lead levels will be offered to locals from next week.
Public Health South is also running a public meeting at the East Otago Events Centre at 7pm on Friday evening for anybody in the community with health concerns.