The Engineering, Printing & Manufacturing Union is forecasting unemployment of 6% over the June quarter.
The Quarterly Employment Survey, which measures job numbers and wages, is due for release on Tuesday.
Another indicator, the Household Labour Force Survey, is due for release on Thursday.
EPMU general secretary Andrew Little, who is also the president of the Labour Party, says the official figures are expected to show a big increase in unemployment compared with the March quarter, when the rate was 5%.
He says many of those who lose their jobs won't show up in the official figures because they have spouses who are working, and this means they don't qualify for the unemployment benefit.
Mr Little predicts more companies will join the Government's nine day work scheme as they seek to retain skilled employees.
