More than 50 migrants - including a six week old baby - were found living in four houses in east London.
A raid by officer from Barking and Dagenham Council found 16 people in a single two-bedroom property, with rooms crammed with beds and mattresses on the floor.
Some of the beds, which were just inches apart, were also found with no duvets or blankets on them.
One property, a two-bedroom terraced house, was found to be occupied by 15 Romanian adults and a six-week old baby girl.
A downstairs lounge at the home had been converted into a third bedroom, with four beds forced into the cramped room.
Multiple sets of bunk beds and mattresses placed on the floor were found in other houses.
At another property, electricity sockets were overloaded with extension cables and the home was deemed to be a potential fire trap.
The homes raided were in Hedingham Road, Lodge Avenue and Bosworth Road in Dagenham and Lyndhurst Gardens in Barking.
Councillor Darren Rodwell, leader of Barking and Dagenham Council, said: “It's actually going back to Dickensian England. It's going back to when we had the slums of the East End.
“We've got to have a really serious talk about how London can accommodate the new people coming in but also the existing people that are already here.”
Barking and Dagenham Council is one of two London boroughs which issues licences to private landlords.
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The aim of the licence, which costs £500 and lasts for five years, is to improve the quality of private rented houses and reduce anti-social behaviour associated with poorly managed rented properties.
A Barking and Dagenham Council spokesman said investigations into the overcrowding are ongoing.