More than 20 men were found crammed into a three-bedroom property during a dawn raid in Kingsbury.
Police raided the semi-detached house in Princes Avenue yesterday morning with officers from Brent’s enforcement team.
Double and single mattresses jammed up against the doors made it difficult for police to gain easy access throughout the house.
The illegal house of multiple occupations (HMO) also had faulty smoke alarms, poor ventilation, insanitary conditions, 26 bed spaces and fire hazards.
Every room, except the gangway kitchen and the bathroom, contained bed spaces, including a tiny, windowless, illegally converted loft space.
The tenants living there told officers they were paying between £30 and £50 a week.
An investigation is under way to locate the landlord or letting agent.
Cllr Eleanor Southwood, cabinet member for housing and welfare reform, said: “We have a zero tolerance policy against landlords who exploit tenants by housing them in slum-like conditions.
“No tenant in Brent should believe that they are powerless against a landlord who takes their money in exchange for squalor.
“We are here to help tenants fight back against rogue landlords by taking them to court.”
From October 1, all properties rented out to five or more people who are not all related will require a licence.
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