Nearly 1000 women have had routine breast screening postponed because of industrial action by mammographers at Dunedin and Southland Hospitals.
Output at the two sites had dropped by a third since mammographers introduced a minimum exam time on August 9.
Southern District Health Board diagnostic and support services general manager Sonja Dillon said 992 routine mammograms had been postponed.
The mammographers' action is part of the nationwide dispute between the radiographers' union, Apex, and District Health Boards New Zealand.
Ms Dillon said urgent mammograms were being carried out within the target time of one to two weeks.
It was impossible to say when the backlog would be cleared, as it depended on how soon the industrial dispute concluded, she said.
Mobile screening units in small centres were unaffected by the industrial action.
The wait for routine CT scans at Dunedin Hospital was 23 weeks at the end of last month, the highest since March 2008.
Wait times for routine scans had been the focus of a special project, which had been successful in reducing them before the industrial action of recent months.
The department had just introduced another efficiency measure, a direct phone link from GPs to the radiology department, which would be especially useful given the current backlog, Ms Dillon said.
Apex southern delegate Bernadette Gourley said the number of postponed mammograms showed how hard mammographers worked, often skipping meal breaks to screen as many women as possible.
She understood there was a particular issue among mammographers relating to repetitive strain injury because of the high workload, although she stressed it was not the reason for the industrial action.
Progress had been made in the long-running dispute, with the two sides reaching an agreement on pay.
Radiographers had accepted 2%, phased over two years, but disagreement remained over conditions and parity issues.
The ball was in the DHBs' court and it was hoped the dispute would be resolved soon.
Some radiographers had left New Zealand in the past few months to work overseas in frustration over the "painful drawn-out ordeal" of negotiating with the DHBs, Mrs Gourley said.
