A report conducted by the BBC has found people living above car repair shops, on industrial estates and in shop storerooms.
In the past nine months, firefighters have attended 36 fires in these makeshift homes – and two people have died.
Tim Rolt, planning enforcement manager for Brent Council, spoke to BBC Radio Four about the dangers people living in these conditions.
“One of the problems we’ve had in investigating this type of accommodation is that a lot of it has been hidden away,” he said.
Mr Rolt also explained that many people living in factories and industrial units don’t speak English very well, and are often reliant on their landlord for work – which makes them vulnerable.
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