Immigration New Zealand is being criticised for using the Christchurch mosque shootings as a "convenient excuse" for visa delays.
Applicants and immigration advisers are being told that prioritising visas for victims' relatives has slowed down its processing times, especially for work visas.
But immigration lawyer Alastair McClymont said it was a distraction to blame the attacks for a long-standing problem.
"The delays started back in November, not 10 days ago," he said.
The consequences of the delays since last year were hurting businesses wanting work visas, he said, but also forcing people waiting on the results of partnership visas to live apart for many months longer.
The delays coincided with the winding down and closure of offices amid an international restructure of how and where Immigration New Zealand processes its visas.
One immigration manager reported staff turnover running at 31 percent, and it was not unusual to have case officers come and go over the course of a residence application being processed, Mr McClymont said.
Immigration New Zealand said it was critical that the right level of scrutiny continued to be applied.
Volumes of applications had been steadily increasing across all visa types beyond forecast volume growth and that had affected the timeliness of some visa decisions.
"We wish to keep our clients up to date and wanted to signal that the Christchurch terror attack may further delay some applications because we are currently prioritising applications for families affected by the terror attack," assistant general manager Peter Elms said.
"Immigration has approved over 300 urgent visas since the 15th March, along with opening up a face to face service for those affected on the ground in Christchurch.
"This has flow-on impacts on the timeliness of work visa applications as Christchurch office primarily processes work visa applications.
"We are doing everything possible to minimise any delays and are committed to processing visas as fast as practicable and generally do a good job of this when the applications are complete and low risk, but processing times will always depend on the complexity of an application."