Hundreds of public servants face months of uncertainty about their jobs because of a large backlog in processing promotion appeals arising from recent recruitment rounds.
The Australian Taxation Office has advised staff that the Merit Protection Commission, which provides independent review of employment actions, has received an "unprecedented volume" of promotions appeals.
"This has resulted in both a delay in candidate notification and forming Promotion Review Committees to consider and determine the merits of an appeal," ATO Assistant Commissioner Megan Boyd has said in a notice to staff.
Jeff Lapidos, secretary of the Australian Service Union Taxation Officers' Branch, said the situation was causing significant anxiety within the ATO.
"Everyone is anxious," Mr Lapidos said.
"People who have been promoted are waiting to hear if they have been confirmed or not.
"Everyone who lodged an appeal against a promotion are keen to find out."
The union leader said that hundreds, "if not thousands", of people were affected.
Mr Lapidos said there was heavy interest in the recruitment round held by the ATO late last year because it was the first it had held for "quite some time", and followed a period in which staffing levels had been run down by redundancies and the imposition of the government's average staffing level cap.
The APS allows for people who have missed out on a promotion to appeal the decision. Reviews are conducted by promotion review committees comprising two MPC nominees and one person from the relevant agency.
The MPC's target is to complete reviews involving fewer than 10 parties within 10 weeks, and those involving more than 10, 14 weeks.
The Merit Protection Commission confirmed it had "recently experienced a significant increase in the number of applications for promotion review...following recruitment activities conducted by various APS agencies".
"Appropriate steps have been taken to manage the increased number of applications [and] we will continue to place priority and resourcing to conduct the promotion reviews on hand as quickly as possible," the MPC said.
Mr Lapidos slammed the commission's response for a lack of detail regarding how long the review processes will take.
"What is happening in effect is that people are being left with no idea about when it will be done," he said.
The union leader said it was extraordinary that the MPC appears to have been caught by surprise by the number of review applications when it should have been aware that hundreds of people had applied for promotions, with the likelihood of a commensurate surge in review applications.
In her notice to staff, Ms Boyd said the MPC was working hard to clear the backlog, but acknowledged the delay had "immediate ramifications" for staff who have been notified of a promotion or are awaiting the outcome of an appeal.
The ATO has advised staff whose promotion was due to take effect this month to report to their new manager on the specified date, and they will be placed on higher duties until April 30.
Those whose promotion entails moving interstate, or who are coming into the ATO from another agency, have been advised to remain in place pending the appeal outcome.
"This approach minimises disruption to our operations and enables us to continue delivering on our commitments to the community and Government," an ATO spokesperson said.