Twenty-six people have been found living in a three-bedroom rental property in an east London borough described as being on the "front line of the housing crisis".
Council enforcement officers inspected the East Ham property on Friday and found that 25 adults and one child lived there. Seven of the tenants resided in a windowless cellar under the house, which had its ventilation duct-taped over.
A Newham Council spokesperson said: "The basement had no windows, so no natural lighting, and inadequate ventilation. It only had one access point through the back garden, not from inside the house."
A number of other "hazards" were identified, along with potential breaches of the Housing Act.
The 26 occupants were from at least four different families and collectively paid over £2,340 rent a month for the property that only had a licence to house a single family of up to seven people, the spokesperson said.
Newham Mayor Sir Robin Wales said the property was a "classic example of the type of exploitation of residents we strive to bring a stop to".
He said: "Twenty-six people living in a three-bedroom property is despicable in 21st century Britain – it’s Dickensian.
“This is the result of the government’s failure to tackle the housing crisis, we need to see more homes being built, as a mixture of tenures so that everyone is society can have a decent place to call home.”
The property had 16 bed spaces and enforcement officers couldn't access two of the rooms, the spokesperson said. It had two toilets but the basement contained no facilities.
Council enforcement officers identified the property through a system that "collates information, including historic complaints and council tax details, to predict whether a property is being unlawfully used as a house of multiple occupation" - but had no idea how big the problem was until they got there.
The overcrowding was the "biggest we have seen for a while", the council spokesperson said.
An enforcement notice was previously issued against the property's owner after she used it for multiple occupation without planning permission. The case was dropped after a subsequent visit by the council in May 2013 found that it had been returned to a standard family rental.
Enforcement officers spoke to a man at the property who lived in a ground floor front room with his partner and young child. The family paid £180 per week, while those in the basement were charged £20 a week each, the spokesperson said.
The man told the council that there were "three or four other families" he was not related to living at the address.
The council is planning on prosecuting the landlord who also owned the property when an enforcement notice was enacted from September 2012.
They will also give her a set time to respond to the issues it identified and if "adequate arrangements to improve" the property are not improved, "a prosecution could be pursued".
Since private rented sector licensing was introduced Newham Council has banned 25 landlords from operating in the borough.
In a speech to the Chartered Institute of Housing conference on Tuesday, Sir Robin said the borough was “on the front line of the housing crisis”.
He continued: “The choice for many of my residents is stark: succumb to rogue landlords – who have no qualms about packing five people to a room and renting out homes without roofs – or leave London altogether, abandoning it to the wealthy and asset-hoarders, leaving our public services without the nurses and teachers we need.”