Mr Jeffries said it was too early to assess the impact of the raft of property and tax changes announced by the Government over recent weeks.
The Rental Price Index measures trends in the expectations of median weekly rents for residential properties on Trade Me Property that have been rented out by real estate property managers and private landlords over the past month.
Around 11,000 rental properties are let out via Trade Me Property each month.
Over the past 5 years, the median weekly rent across New Zealand has risen by 23.5 per cent from $340 per week in April 2010 to $420 per week last month. Mr Jeffries said the majority of this $120 per week increase had occurred since the middle of 2013.
Four regions reported double-digit rental growth in the year to April 2015. Leading the way was Gisborne (+20 per cent), followed by Marlborough (+12.3 per cent), Bay of Plenty (+10.9 per cent) and Southland (+10.0 per cent).