A bed in a bathroom of an illegal accommodation in the Sydney CBD. Credit:City of Sydney "Our staff who have attended inspections have been verbally threatened and abused," she said. "Evidence we've recently collected suggests multiple offences are taking place, some of which are outside councils' powers and responsibilities. This means a multi-agency approach is the best way to disrupt operations and deter new operators."

A bunk bed in a laundry of an illegal accommodation in the Sydney CBD. Credit:City of Sydney The squad is headed by Roy Cottam, a former Scotland Yard detective with specialist skills fighting organised crime. He is flanked by members who have served in the NSW Police Force and the Royal Australian Corps of Military Police. "Properties that are significantly overcrowded, with unauthorised building works and fire safety defects, are our investigative priority and the area where we'll take immediate action due to the higher safety risks and negative impact on other residents," he said. A makeshift shower in the hallway of an illegal housing set-up. Credit:City of Sydney "We want to send out the strong message – we are coming after you."

In July last year, a ferocious blaze at the back of a small factory complex in Alexandria uncovered a squalid, illegal housing set-up. At least 15 Japanese and Korean nationals were charged up to $160 a week by landlord Masaaki Imaeda to live in shipping containers, a graffiti-riddled bus with no wheels and decrepit caravans stacked on top of each other. When questioned by Fairfax Media whether Mr Imaeda had been fined, a City of Sydney spokesperson refused to respond, saying: "We can't comment on current investigations. This one is ongoing." Stephen Goddard, chairman of the Owners Corporation Network, applauded the council, saying apartment owners had felt powerless for too long. "Initially the problems were with short -term letting, which expanded with backpackers, which then expanded with overseas student accommodation. It's escalated over time," he said.

"It reflects the rising cost of living in Sydney and population compression. It's a relief to know one tier of government is doing something." Kristy Carstairs, president of the Backpackers Operators Association of NSW, said she was relieved it was not a death or injury that sparked concrete action. "CBD high rises are notorious for overcrowding ... the five very central CBD blocks around the Town Hall area would be the worst. It's inner city locations or close to universities. Foreign students are a target," she said. Fire and Rescue NSW superintendent Mark Reilly called the overcrowded units "dangerous".

"Overcrowding, blocked exits and unauthorised modifications can jeopardise the safety of residents in these buildings. We often see these sorts of unauthorised modifications compromise the effectiveness of in-built safety features like sprinklers and smoke alarms," he said. A Fairfax Media investigation in 2013 uncovered rampant overcrowding and illegal renovations in inner-city apartment blocks, finding three examples after contacting just eight "room-for-rent" advertisers. Beds were offered for $130 to $175 a week. In areas around Macquarie University in North Ryde, up to 20 students were hot bunking - sharing beds alternating different times of the day and night.