Children sleep within inches of fungi growing through walls. Immigrants live illegally in sheds in other people's back gardens. These are just two examples of the rise of slum housing in Britain, as individuals and local authorities struggle to cope with a 21st-century housing crisis which has led to unscrupulous "slum landlords" profiteering from society's most vulnerable.
A chronic shortage in social housing and an unaffordable housing market mean that around 3.4 million people in the UK rent their homes, a 40 per cent rise in the past five years.
Local authorities are turning a blind eye to illegal and unsafe housing because they do not have the resources to re-house those inside, housing officers admit in footage obtained by uncover documentary teams for Channel 4's Dispatches.
Dr Julie Rugg, from the Centre for Housing Policy, who was commissioned by the Labour government to review the private rental sector explained: "An environmental health officer might say, 'Look, 60 of these properties... I could condemn them tomorrow... but where are these people going to go?'
"The ability of the environmental health officer to react is undermined and in some cases they get actually quite dispirited because they know that other parts of the council aren't going to take any action."
The programme exposes the practices of unscrupulous landlords who evict people from their homes in order to charge new tenants higher rates, and whose properties fail to meet the most basic standards required by law – yet authorities seem unable to take action.
The programme, presented by Jon Snow, also reveals communities of illegal immigrants living in garden sheds in Southall, West London.
An undercover reporter pays £40 a week in cash to share a shed in a back garden with a stranger, in which the wiring is unsafe, putting their lives at risk. In the house itself, the landlord rents a room to an Indian family comprising two adults and two children. The children are continually bitten by bedbugs.
Campbell Robb, chief executive of homeless and housing charity Shelter, said: "Many environmental health officers tell us they see problems all the time. They don't have the powers or the capacity to do something about it. Let's be frank, the cuts that many councils are going through at the moment, this is one of the areas that is going to suffer most."
Research conducted by Shelter says that more than 90 per cent of environmental health officers with tenant liaison responsibilities have encountered examples of landlords engaging in the harassment or illegal eviction of tenants.
Eighty per cent of environmental health officers have come across landlords in their area who persistently refuse to maintain their properties to a decent standard and yet two-thirds say no landlords have been prosecuted in the past 12 months.
Mr Robb said: "The Government has to recognise its responsibility to protect this vast and growing population of private tenants.
"We urge the housing minister to work closely with all local authorities and ensure that they are using every weapon in their armoury to crack down on unlawful operators, like those exposed in Dispatches. It is absolutely essential that we are sending a clear signal to tenants, landlords and local authorities that enforcing the law against rogue landlords is a priority."