Figures released by Trade Me show 35 people were interested in another house on Leith St in Morningside in April.
New Zealand's national median rent reached a record-breaking $475 a week after a 5.6 per cent jump on April last year.
Tasker, president of the Northland Property Investors' Association, said rents reflected what tenants were prepared to pay.
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"I believed it's 100 per cent market driven. I remember a few years ago, I had to drop $40 [a week] off so that people could move in," he said.
Tasker owns nine rental properties throughout Whangārei and he said that since more people were moving to New Zealand than we could build houses for, properties became less affordable to buy as well as to rent.
Tasker said it was also difficult for landlords to buy more rental properties.
"If the Government hadn't put a 40 per cent deposit rule for landlords to buy houses and rent them out, there'd be a hell of a lot of rental properties on the market."
He said people buying former rental properties to live in them also contributed to a shortage of rental houses.
Head of Trade Me property Nigel Jeffries said the greater demand for rentals than supply in Northland was unusual at this time of the year.
"Typically, in the autumn months we see rent growth slow right down but this year Northland bucked the seasonal trend and we've in fact seen rent prices increase in April."
Anecdotally, he said, across New Zealand more owner-occupiers were buying ex-rental properties to live in and a similar trend was seen in Northland.
"Looking ahead to winter, it seems we're going to continue to see excess demand in Northland which will most likely lead to small but continuing rent increases," Jeffries said.
The Far North saw a fall in the median rent, from $380 to $360, while Kaipara remained static at $400 over one year.
Paul Beazley, of LJ Hooker in Whangārei, said demand for rental properties was pretty strong - not just in suburbs closer to the city such as Kensington, Regent, Morningside and the Avenues but also areas like Onerahi and Tikipunga.
"In the past two to three years, a lot of rental properties have been sold to owner/occupiers while there hasn't been any new builds specifically for investment in Whangārei in the last 10 years," he said.
Like Tasker, he thinks the demand for rental properties in Northland will stay stronger for some time.
Beazley said some landlords decided to sell their rental properties ahead of changes to the Residential Tenancies Act that would have increased their compliance costs.
Landlords have until July 1 next year to insulate their rentals under the act. The Government estimated 180,000 properties would need new insulation to comply with the deadline to make rental homes warm, dry and safe. Landlords not complying face a fine of up to $4000.
