The World Health Organisation (WHO) has admitted it got details of air pollution levels in Auckland wrong.
Data released by the WHO claimed Auckland's air pollution was double that of Sydney and as bad as Tokyo.
It said the air quality measurement for Auckland was 23 micrograms of pollutants per cubic metre of air.
Now it says the figure is 15 micrograms, still at variance with the government's official reading of 16.
The WHO also said air pollutant levels in Wellington were twice that of official New Zealand figures.
It says it sourced its figures from the Ministry for the Environment website in February.
But a spokesperson for the Environment Minister, Nick Smith, says the ministry's air pollution figures have been online since October last year.
The minister's office is investigating.