Calls to Tenancy Services have jumped by more than a third in the past month compared to late last year.
The surge is partly down to a seasonal peak in fixed-term tenancies ending but also changes to rental laws, including no-cause evictions, coming into effect last month, Tenancy Services spokesperson Steve Watson said.
Landlords are also contacting the services for advice in the lead-up to the Healthy Home Standards deadline approaching in July, he said.
Total calls in February jumped by nearly 17,000 calls compared with November last year.
A Christchurch renter who has been plagued with problems in her home is frustrated she can't get through to Tenancy Services to complain.
The renter, who RNZ has agreed not to name, said her property manager had failed to fix significant problems with mould and dampness, which is making her sick.
Rain coming through a crack in the side of the brick house had "ruined" the lounge and caused the paint to warp and mould to grow, she said, adding that when she raised the problem with the property manager, he told her to "go get a bucket with bleach and start scrubbing".
The property manager told her to air out the rooms to avoid further moisture in the air, but as it was winter, that only made the situation worse, she said.
"My respiratory system has been deteriorating over the year, same with my flatmates, and when we take time off work to try and get better, we have to do it in this house, which doesn't help."
She has tried calling Tenancy Services but has either been cut off, told the line is too busy.
"Most of the time I get put on hold for over an hour, or the line is too busy and it disconnects me. It seems really impossible."
The situation with the property manager, and now Tenancy Services, has left her feeling demoralised and helpless.
"It has hit me really hard mentally because I have found trying to get help very difficult and it's a long process."
Tenancy Services said staff are aware of delays and are looking to improve its services.