The Electrical Safety Council (ESC) found that a fifth of tenants, equating to 1.7 million private renters across the UK, have reported concerns about the electrical safety of their property to a landlord that were either acted upon slowly or not dealt with at all.
The charity urged landlords to make sure they comply with legal obligations to ensure that electrical installations and wiring are kept in a safe condition throughout the tenancy. Failure to do so means that landlords could end up having their insurance invalidated or be fined tens of thousands of pounds.
Tenants also have a responsibility to maintain the electrical items they bring into the house and should report hazards to their landlords immediately, the ESC said.
The findings come at a time when interest in the buy-to-let sector from landlords has been increasing due to strong demand for private rental accommodation from tenants which has pushed up rents. Many people have also become "accidental" landlords because they have found it hard to sell their home in the difficult economy.
"We need all landlords to understand that they are not only putting people's lives at risk, but they could also face serious financial loss through fines or invalidated insurance if they don't act on their existing obligations."
Kay Boycott, director of campaigns, policy and communications at Shelter, said the charity hears from families "across the country" who are living with the knowledge that an electrical fault in their home is putting their safety at risk.
More than 4,000 people took part in the ESC's research across the UK. The ESC has produced a free smartphone app called "home electrical safety checks" to help people make sure that each room in their property is safe.
A guide for landlords and tenants on their electrical safety responsibilities can be viewed at esc.org.uk/landlords.