Canberra's rental market remains the most expensive capital city for tenants, according to the latest report from Domain.

Rents over the first quarter of the year increased by 3.4% to $600 for houses and 4.2% to $500 for units.

These increases have the pushed price gap further from Sydney, with Canberra unit rents now $30 more than the Harbour City. Furthermore, house rents in Canberra are $50 more expensive than the next most expensive cities, Sydney and Darwin.

"Tenants have been operating in a landlords’ market for some time, and landlords are likely to have become accustomed to the fierce competition to secure a lease," said Nicola Powell, senior research analyst at Domain.

The rent increases could be due to the tight conditions of Canberra's rental market. In fact, vacancy rates in the city have fallen further in March to 0.7%, hitting levels similar to the conditions in 2018.

"Tenants will find the task of securing a lease harder, as the estimated number of vacant rentals continues to decline, 14% lower than last year," Powell said. "This is during a time when Australian expats return, temporary overseas employees extend stays, and the city is better placed economically, buoyed by the public sector and industries reliant on government spending."