The Union of Kanak and Exploited Workers says it will boycott the forthcoming population census in New Caledonia unless a question on ethnicity is included.
The census was postponed last year after the French President Jacques Chirac said it was irresponsible and illegal to include questions about ethnic origin.
The question was taken out and the new census is now expected to take place in three weeks time.
But the executive member of USTKE Pierre Chauvat says that will make it impossible to keep track of how many people are moving to New Caledonia from France.
Mr Chauvat says this means more jobs are taken from Kanaks and efforts to reach independence are blocked.
"By flowing people into this country heavily means that in another five, ten years the Kanak will not be in majority in this country and therefore the questions of independence will be thrown away."
The executive member of USTKE Pierre Chauvat