Local authorities could force property owners to repair homes or face prosecution under the 2004 Housing Act.
Hazards qualifying for Category 1 under the Housing Health and Safety Rating System include those that can cause death, lung cancer, permanent loss of consciousness, 80% burn injuries, the loss of a hand or foot, eye disorders, heart attacks and poisoning.
The English Housing survey states that in the UK, almost five million dwellings contained such hazards and that 1.9 million dwellings contained dangerous steps and stairs.
Stuart Pearce, chief executive officer of SearchFlow, said: “Many homeowners are unaware they live with serious hazards every day.
“When private dwellings are assessed by local authorities, there’s a one in five chance there will be a hazard present which requires immediate attention.
“This is a cost most property owners don’t factor into their plans and can therefore prove very hard to deal with.
“If you don’t make the required repairs, even if you can’t afford to, local authorities have the power to issue prohibition orders, which mean you aren’t legally allowed to live there any longer. In this situation, the only option for the owner may be to sell at a knockdown price.”