One million rented homes in England 'are dangerous'
Around one million privately let homes in England are so substandard they are dangerous, the Chartered Institute of Environmental Health (CIEH) has said.
The organisation has warned those figures are set to rise, citing a lack of social housing, and cuts to housing benefit and legal aid.
Councils say they are doing what they can to tackle the problem but argue clear, workable legislation is needed.
The government said more red tape would harm tenants' interests.
Local authorities in England have said their hands are tied because proposals they thought were going to help the situation - such as a national landlords' register - have been scrapped by the coalition government.
The CIEH said unscrupulous landlords were exploiting the lack of rented accommodation, and there were fears that cuts to housing benefit could make the situation worse and force tenants to live in unsafe buildings, often with exposed electrics, mould and damp.
The number is expected to rise due to people not being able to afford to buy homes, while local authorities push people into the private rented sector as they try to tackle waiting lists for social housing.
Chairman of Local Government Regulation, Councillor Paul Bettison, said there was "clear evidence" that councils were cracking down on rogue landlords.
"However, at a time when councils are facing the worst financial settlement in living memory, having clearer and more workable legislation would be beneficial.
"With the limited resources available to councils at present, the introduction of a national landlord register would certainly help councils further in tracing those breaking the law."
The BBC's Keith Doyle said government figures showed 1.5 million - nearly half of all privately rented homes in England - were substandard, with one million classified as dangerous to live in.
A Communities and Local Government spokesperson said ministers believed the current system struck "the right balance between the rights and responsibilities of tenants and landlords".
"Tying the whole sector down in red tape will harm tenants' interests by pushing up rents and reducing the choice of properties to rent.
"Councils have a wide range of powers at their disposal to tackle the minority of rogue landlords who fail in their responsibilities.
"We are working with them, to ensure that any barriers to their using those powers, are lifted," they added.
While there is no central regulation system for private landlords in England, Scotland has landlord registration, designed to help councils monitor private landlords and ensure that they are suitable people to let out property.
Failing to apply to the local council for registration is a criminal offence, but last year charity Shelter Scotland said rogue landlords were continuing to operate three years after the scheme was introduced, with one in four rented properities not registered.
The Welsh Assembly Government has powers over housing through the Local Government and Housing Legislative Competence Order (LCO), which was given Royal Assent last year.