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.
Closures and reduced work hours were also taking place in other areas, the union said.
Reid said action from the Government was needed to stop any further decline in the industry.
"It is no good to hope and wait for local timber to be used in the Canterbury rebuild if there are no processors left to manufacture the wood required."