New data has dealt another heavy blow to those looking to rent, with the number of properties for rent in Sydney the lowest it has been in over a decade.

PropTrack's latest Rental Listing Market Insight report shows that the number of new rental listings on realestate.com.au fell by 17 per cent in April, reaching its lowest level since April 2012.

Meanwhile, the total number of rental listings on realestate.com.au across Harbour City fell by 7.8 per cent in April, hitting another low since December 2012.

PropTrack's director of economic research Cameron Kusher said that while April was a notoriously down month for rental listings, the decline across Sydney was "on the large side".

"The bigger takeaway we saw was that the total number of properties available for rent in Sydney fell by another 15.7 per cent from 12 months ago," he said.

"This highlights how difficult it is for renters to find accommodation."

Mr Kusher said the shrinking number of rental properties in Sydney, as well as the number of new listings, was a concern.

"If you look at the situation now, the number of properties available for rent is down 42.7 per cent compared to the start of the pandemic," he said.

"These conditions are ripe for landlords to put rents up and people are unable to find properties available to rent."

However, he said the report showed that total rental properties in the city and inner south and eastern suburbs had increased during the month.

"There were fewer new listings, but a bit more total rentals," he said.

"But generally speaking, across Sydney, particularly in those inner city areas, the number of properties available for rent is down significantly compared to a year ago."

In the past 12 months, property rentals across the eastern suburbs have fallen by 21.2 per cent, while those in the inner south-west have fallen by 34.1 per cent, those in the inner west by 27.4 per cent and those in Parramatta by 29.6 per cent.

However, Mr Kusher said that on the flip side, areas such as Baulkham Hills, Hawkesbury, Blue Mountains and Central Coast now have more properties on the market for sale than they did 12 months ago.

"We're definitely seeing some easing in rental prices in the suburbs of the city, but rents have tightened up quite a bit in the inner and central ring, particularly in areas close to universities," he said.

A key finding of the PropTrack report is that without an imminent increase in supply, the number of rental properties will remain low and push up the competition faced by renters.

"Unfortunately, there is nowhere near enough supply," Mr Kusher said.

"I would be very surprised if there is any relief in the next few months. You have a lot of housing being built, but most of it is for owner-occupiers. Rent-to-own is coming, but it's a premium product and there's not a lot of it.

"You still have a lot of people selling their investment properties and we know there are still a lot of people coming into the country from overseas.

"Another important factor is that it is difficult for people to make the leap from renting to buying their first home. Although rents are rising rapidly, it is still generally cheaper to rent than to pay off a mortgage."

He said the risk of people becoming homeless was also increasing, especially those who were out of work and on government support payments and essential workers.

"I know that rent bids are not allowed, but the reality is that if you can afford to offer a higher rent than advertised, you have a better chance of getting a property," he said.

"Unfortunately, people on lower incomes don't have that luxury."

The report shows that the number of new rental listings in the NSW region is also falling, down 17.2 per cent in April.

However, the number of new rental listings has increased by 23 per cent compared to April 2022.