The National Australia Bank announced to the stock exchange on Tuesday 1500 jobs will be axed before the end of 2026.
The timing could not be worse for workers, who were already buckling under massive workloads and unrealistic targets, Finance Sector Union national assistant secretary Nicole McPherson told reporters.
"We have real fears about the financial security of workers at NAB and their wellbeing, given that these 1500 job losses are going to be right on the eve of Christmas," she said.
"The remaining 1000 workers will have to wait in limbo until sometime in the new year to see if they have any job at all."
Most workers were told of the redundancies by email on Tuesday morning, the union said.
"The lack of detail provided by NAB has only compounded worker anxiety, with no one knowing exactly which areas of the business are going to be targeted," Ms McPherson said.
A total of 2500 staff - or about six per cent of the bank's workforce - are set to go over the full financial year.
The move was designed to make the bank more efficient and would have no material impact on customer-facing positions, NAB chief executive Andrew Irvine said.
''These changes are expected to improve outcomes for customers by reducing duplication and speeding up decision-making,'' he said in a statement to investors.
''We know this will be a difficult period for our colleagues impacted by these changes as well as the people around them."
The bank will also reduce its use of consultants and external contractors.
Union officials met with NAB on Tuesday to question whether AI was behind the planned job cuts.
"They said they would need to come back to us," Ms McPherson said.
The cuts were expected to result in restructuring costs of about $300 million in the 2027 financial year, NAB said.
In May, the bank reported a near-20 per cent fall in 2026 first-half statutory net profit, although its preferred metric of cash net profit - which excludes large items - was flat at $3.59 billion against the same period a year earlier.
NAB's result was supported by strong growth of 5.4 per cent in its business and private banking arm and a higher net interest margin, which reflected its earnings on lending activity.
The job cuts raised broader questions about what was driving the restructure, Swinburne governance expert Helen Bird told AAP.
She said transparency was needed on whether AI would replace the job losses.
"Transparency is absolutely vital and you have to be really honest from the get-go, so there are no illusions about what's happening here," Ms Bird said.
"This is no doubt an early example of the large-scale employment cuts we will see in the coming years."
Ms Bird said NAB needed to explain how cutting thousands of roles would deliver the efficiency.
The bank is the latest to announce sweeping job cuts, after rival ANZ drew widespread criticism for its "unhinged" decision to cut thousands of jobs.
ANZ announced in 2025 it would slash 3500 staff and 1000 contractors by September 2026 as part of a $560 million plan to simplify operations.
Bendigo and Adelaide Bank has also been preparing to axe 140 jobs across the company, according to the union.