A London local authority is looking for the landlord of a bungalow which had two bedrooms but was home to 15 men.
Brent council discovered the overcrowding in a raid on the property.
The tenants were found sleeping on mattresses strewn across the dining and living room floors, as well as on bunks and beds.
The council says conditions were so cramped that the renters had resorted to storing clothes and shoes in furniture protected by tarpaulin in the back garden.
The men, who were paying £50 a week each to live in the chronically overcrowded property, were plagued by damp, mould, poor ventilation, a broken soil stack, damaged light fixtures, poor maintenance and unsafe living conditions.
The local authority also claims safety was compromised by the fact that there was no fire safety system inside the property.
The tenants' rent added up to £3,250 a month; twice the amount shown on the tenancy agreement.
A council spokeswoman says the conditions were “appalling”.
“There are no circumstances in which it is okay for people to have to live like this - in unsafe, squalid conditions. That's why we expect landlords to license their properties and why we're prepared to take the strongest possible action, including through the courts, if they fail to do so” she says.
"There's no excuse for landlords not to know who is living in their properties. It's their responsibility to make routine checks. We will continue to crack down on landlords who refuse to manage their properties properly."
Officers from the same council also raided a second unlicensed property.
They discovered five households sharing one kitchen, bathroom and toilet between them. The 11 tenants, which included two children, were paying £1,750 in order to live in the unlicensed house in multiple occupation