The chief census officer in New Caledonia says the decision by some political groups to boycott the survey will have an effect on the results.
Gabriel Gamblin says the census will probably be two or three per cent short of the true population figure.
Two unions and the Palika faction of the Kanak separatist group F-L-N-K-S have told their members to boycott the census, because the questionnaire doesn't ask respondents for their ethnic identity.
During a visit to New Caledonia last year, the French President, Jacques Chirac, said that asking people about their race would be scandalous and unlawful.
But opponents want an accurate assessment of the number of indigenous people living in the French territory in order to ascertain whether their voting power is being watered down.