Lord Mayor Clover Moore has announced the council is redoubling its efforts to stamp out illegal accommodation, establishing a "heavy hitting" team with former members of Scotland Yard and the Australian military police.

Since March, the squad has executed 22 search warrants, uncovering 58 beds crammed into a three-bedroom house, makeshift showers in hallways, and tenants sleeping in bathrooms, pantries, and stairwells.

NSW Police Force Acting Commander Anthony Bell said the squalid set-ups - often illegally subdivided, unsafe and overcrowded - were linked with crime, such as theft and drug use.

"In one of the recent matters in Pyrmont, there have been issues of unreported violence occurring inside for a number of months," he said.

"We know from the crime and the other activities that occur in these premises that by shutting down these premises, we are able to be more proactive in addressing crime issues across the greater city."

Ms Moore said the syndicates were becoming increasingly sophisticated and hostile, refusing access to council officers trying to gather evidence that could lead to legal action.

The Unauthorised Accommodation Investigation squad is targeting organised networks and adopting a multi-agency approach, joining forces with NSW Police, Fire and Rescue NSW and NSW Fair Trading.

"Our staff who have attended inspections have been verbally threatened and abused," she said.

Squad leader Roy Cottam, a former Scotland Yard detective with specialist skills fighting organised crime, said they were in the midst of collecting video and photographic evidence to launch legal action against slumlords.

"We're finding it's price per bed instead of bedroom. If you have 10 to 14 people in a one bedroom apartment, they're paying $130 to $150 each per week," he said.

"[The landlords] usually advertise using free mediums, such as Gumtree, Facebook, mobile apps and lamp posts ... We're going to come after you."

Fire and Rescue NSW superintendent Mark Reilly said illegal accommodation risked the lives of tenants, neighbours and firefighters.

"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.

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."

Ms Moore conceded a large factor driving the illegal accommodation boom was Sydney's unaffordable housing.

"It's something the city has been concerned about for a long time. We want to see them working with state and federal governments," she said.

But City of Sydney Labor councillor Linda Scott said the mayor had failed to address the housing crisis for a long time.

"After years of broken promises and lack of action, it's hypocritical for the Lord Mayor to be attacking the outcomes of the Sydney housing crisis, without addressing its causes," said Linda Scott.

"She has been woefully inconsistent on delivering new affordable housing. In 2008 she committed the City's Bay Street Depot to the Glebe Affordable Housing Project, and yet over seven years later, the City has cut $20 million in funding for this project."

The squad has so far discovered: "kitchens with serious cockroach infestations", "blocked drains full of excessive amounts of hair and putrid smells in all rooms" and "disconnected smoke detectors."

It will also target real estate agents suspected of working with slumlords.