Higher house sale prices in the region have also led to higher rental prices, Mr Beazley said.
Trade Me reported that sale prices in Northland were up 20.6 per cent in the year to December 2016.
Median rental prices last month were $352.50, compared to $327.50 in January 2016.
Rental prices for units in the region have risen 20.8 per cent over the same period, from a median of $240 to $290 per week.
Renee Wilkinson, new business consultant for Harcourts Whangarei, said the agency was getting "lots of enquiries" for the available rental properties.
The agency's own statistics show an average asking price for new rentals of $404 in Whangarei last week.
The shortage was simply because "a lot of people are relocating to Whangarei", Mrs Wilkinson said.
Rental prices increased in all other regions except Canterbury, the West Coast and Taranaki.
Hawke's Bay and Waikato had the highest rent increases in the country, of 12.5 and 11.4 per cent respectively.
Median rents in Wellington reached a record high of $480, and the number of rental properties available there declined by 70 per cent in the last year.
One advertised property received 350 enquiries from prospective tenants in one week.
Real estate agents in Rotorua and Whanganui have also reported shortages of rental properties.