Griffith University labour economist Professor David Peetz said the wage growth falls were across many industries and states.

"That suggests to me that it's not just a quirk of the data," he said.

However, he said the falling behind of union pay rises to non-union pay rises, while significant, "occurs only once in a blue moon".

"I don't expect that pattern to continue, and so I'd expect wage increases in union EBAs to bounce back up to some extent, or for wage increases under non-union EBAs to go down further.

"Overall, though, it continues the current story of very low growth in wages."

Non-union pay increases have been relatively stable over the last year, recording 2.5 per cent in each of the last five quarters.

However, public sector increases, which mostly cover unions, suffered dramatic falls in the September quarter as pay increases fell from 2.5 per cent in June to a historic low of 2 per cent.

Industries with lowest wage increases were real estate services, transport and warehousing and administrative services.


The construction industry remained the sector with the strongest wage growth but it dropped back to a 24-year low of 3.1 per cent.

UBS economists George Tharenou and Carlos Cacho said the data showed underlying wage pressure had weakened further and that wage growth estimates from Treasury and the Reserve Bank were still too optimistic.

Labor leaped on the wage data to argue it was due to unions' "dwindling bargaining power" and accused the Turnbull government of facilitating it.

"The data released today is more confirmation, if any was needed, of this link," opposition shadow spokesman Brendan O'Connor said.

"Labor is seriously concerned the Turnbull overnment is incapable of addressing consistently flat wages growth – and in fact they're making things worse by cutting the penalty rates of Australia's lowest paid workers and by their abject failure to address the decline in enterprise bargaining."

New industrial relations minister Craig Laundy was not available for comment.