Environment Minister Nick Smith is questioning a claim that Auckland's air quality is worse than Sydney's and the same as that in Tokyo.
The World Health Organisation (WHO) compiled data measuring the amount of fine particles of pollution in the air in more than 1000 cities in 91 countries.
Dr Smith says Environment Ministry staff have reviewed the data and do not understand how the conclusions for New Zealand were arrived at.
Preliminary analysis shows the annual averages reported by WHO are in most cases much higher than the Environment Ministry reports.
The WHO report said that 2009, Auckland had an annual average of 23 micrograms of PM10 particles - pollution less than 10 micrometres that can penetrate the lungs and enter the bloodstream.
The ministry's preliminary data put the figure at 16 micrograms of PM10 particles.
The ministry's figures for Hamilton, Wellington and Christchurch figures were also lower, but for Dunedin were 20 micrograms of PM10 particles compared to the WHO's 19 micrograms.
Dr Smith says Ministry officials have contacted the international organisation and are waiting for a response.
He says Auckland does have air pollution problems, which the Government is working to solve, but the situation is not as bad as in the WHO figures.