Investors with properties in Perth should be doing all they can to keep their tenants happy after the city saw a spike in its rental vacancy rate.

Figures from the Real Estate Institute of Australia (REIWA) show that in the three months to May this year Perth’s rental rose to 4.9%, the highest it has been in almost six years.

The city’s vacancy rate had not topped 4.8% since September 2009.

The last month alone saw 600 rentals become vacant, pushing the total out to 8,147 homes looking for tenants in Perth.

REIWA president David Airey said the rise in vacancies was due to a combination of over-supply and a slowdown in population growth and it was causing rents to fall.

“The long term equilibrium for Perth’s vacancy rate is 3 per cent, so the current situation means there are more than 50 per cent more properties on the market than is usual,” Airey said.

“The competition among property owners is having an effect on price, with the metropolitan median rent dropping by $5 on the March quarter to $425 per week, which represents a cut of $25 on the same time last year.”

According to the REIWA figures, Perth’s median rent peaked at $475 per week in the middle of 2013, but has since fallen by around 10%.