The days of relying on neighbours to dob in landlords who have illegally crammed tenants into houses and apartments may soon be over.

Instead the NSW Government will harness big data to crack down on illegal boarding houses across Sydney.

Information from sources such as the electoral roll, utility bill companies as well as complaints from Fair Trading, will be collected and used to find where more people are living than is being claimed, Minister for Innovation and Better Regulation Victor Dominello told Domain.

The project from the NSW Data Analytics Centre uses a Big Data approach, where many sets of information are collected and interpreted to fit the puzzle pieces together, Mr Dominello said.

“By comparing the water use for a standard two-bedroom apartment with one that has many residents could be the first alert of an illegal boarding house,” he said.

[Illegal accommodation is] an indication of how dysfunctional our housing system is.Ned Cutcher, Tenants Union NSW

With the addition of complaints made to Fair Trading, a compelling case that the home might be an illegal boarding house could be built.

“If you know the Big Data, then, rather than knocking on 100 doors, we can do 10 targeted homes and it’s likely a slumlord will be behind one of them,” he said.

In authorised boarding houses, a maximum of two people can share a bedroom at the request of a resident. A room for one person should be no smaller than 7.5 square metres, or 11 square metres for two people.

In illegal boarding houses, four people may share the same sleeping area and partitions may be created using shower curtains to turn living rooms into bedrooms.

For Mr Dominello, it has been a long journey towards better enforcement against “horrendous practices that can be devastating to the community”.

Since doorknocking in 2008 alerted him to slums operating in his electorate of Ryde, he was instrumental in creating the Boarding Houses Act 2012 to create a registration program for boarding houses and bringing in basic standards.

“This is still a serious issue, particularly in highly developed areas,” he said.

Sometimes, the location of illegal accommodation is only revealed after disaster strikes.

At the moment, councils rely on neighbourhood complaints, circumstantial evidence and door-knocks to find slums. Complaints often come from neighbours of overflowing bins, or unkempt homes, while stuffed letterboxes can also be a sign.

In May 2015, the City of Sydney established a dedicated investigation team to identify illegal accommodation operators across their council area.

Over the past 12 months, they led 30 search warrants and carried out 30 suspect interviews. The evidence is being used to formulate two cases, a spokesperson said.

About 100 premises have been inspected in the local government area. In one investigation, 58 beds were found crammed in a three-bedroom house in Ultimo, including a bed in the bathroom and laundry.

In 2015, a City of Sydney investigation found a bed in a bathroom of an illegal accommodation in the CBD. Photo: City of Sydney

“The team has issued fines totalling $75,000, and is currently undertaking criminal proceedings in the NSW Land and Environment Court in relation to unauthorised use of an industrial estate for short term accommodation,” they said.

Tenants Union of NSW senior policy officer Ned Cutcher said boarding houses threatened overcrowding, health problems and safety issues for marginal renters.

“​People working in tenancy advice and advocacy services find [tenants subject to] interpersonal problems, assault and inappropriate treatment,” Mr Cutcher said.

Tenants of these situations would also find their rights falling under Common Law, meaning they would be unable to go to Tribunal to solve their issues and would have to fund a case through the Supreme Court. For most, the expense could make it “difficult to recover the money paid” as a bond.

“[Illegal accommodation is] an indication of how dysfunctional our housing system is,” he said, pointing to affordability issues that push people into overcrowded rental situations.

A review of boarding houses legislation is scheduled to take place in 2017.