The National Distribution Union says figures from Statistics New Zealand confirm its concerns about the state of the wood industry.
Statistics NZ's Economic Survey of Manufacturing says the volume of wood and paper product sales declined 0.8 per cent in the June quarter.
Seasonally adjusted sales volumes fell in four out of the last five quarters, the survey says.
The union said that despite "upbeat talk" at a wood industry conference in Rotorua last week, it had expressed concern over falling production, sawmill closures and job losses.
General secretary Robert Reid said the union had dealt with several cases of wood processing workers losing their jobs in the past few weeks in Kawerau, Tangiwai and Fielding.