More than 10,000 manufacturing workers and over 13,000 builders left New Zealand during the last three years, new figures show.
The Greens say most of them went to Australia and the exodus has created a skills shortage.
Co-leader Russel Norman is citing data in Statistics NZ's International Travel and Migration Survey, released on Thursday.
"If companies do look to hire, they are finding many of the skilled workers have left for Australia," he said.
"This loss of talent is stifling companies' ability to grow and hampering economic recovery."
Labour's finance spokesman, David Parker, accuses the government of failing to protect jobs and says it might as well hand out boarding passes.
"There are 175,000 Kiwis looking for work in New Zealand, many of whom will be giving serious thought to joining their countrymen across the Tasman," he said.
Labour, the Greens, NZ First and Mana have launched a parliamentary inquiry into what they say is a crisis in manufacturing.
The government says there isn't a crisis.