UPDATED 12.12pm: Landlords are dismissing suggestions that rent hikes are unnecessary with falling interest rates.

The council has announced an average residential rates increase of 9.9 per cent - due to come into effect next month.

The latest Crockers Property report shows more than three quarters of landlords in Auckland are preparing to put rents up to cover hefty rates increases planned by Auckland Council.

Of the 127 landlords surveyed, only a quarter of landlords indicated that they would not increase rental prices to cover the rates hike, with the remainder increasing prices to cover all (33 per cent), or part of the increase (43 per cent).

Numbers released by TradeMe Property today show rents in Auckland have increased by 6.5 per cent in the year to May 2015.

Rental increases are slowing in most of the country with the national median rent hovering at $420 since January.

Trade Me Property's Nigel Jeffries said Auckland tenants were now paying at least $3500 more than tenants nationwide.

"It's an all too familiar scenario for those renting in the Super City - we've seen the average price of houses explode and the rental market continues to follow a similar trajectory," he said.

Property Investors Federation spokesman, Andrew King, said there is a raft of expenses which need to be recouped.

"Some people would say that interest rates are coming down and maybe that compensates, but when interest rates go up rents don't go up to cover interest rates so it's not really fair to say that."

The bump in prices has bucked the national trend, reaching a median weekly high of $490, TradeMe data shows.

May had been the "weakest" month for median rent prices in New Zealand but that did not mean it was cheap, he said.

The weakest region in May was Gisborne, which was down 9.2 per cent compared to 2014, followed by Otago, which was down 6.3 per cent.

The TradeMe Property Rental price Index measures trends in expected weekly rents for residential properties on the site, with about 12,000 rented every month.