Investigators have warned consumers they face potentially fatal risks after 99 per cent of fake Apple chargers failed a basic safety test, reports BBC.
Trading Standards, which commissioned the checks, said counterfeit electrical goods bought online were an "unknown entity".
Of 400 counterfeit chargers, only three were found to have enough insulation to protect against electric shocks.
It comes as Apple has complained of a "flood" of fakes being sold on Amazon.
Apple revealed in October that it was suing a third-party vendor, which it said was putting customers "at risk" by selling power adapters masquerading as those sold by the Californian tech firm.
The Trading Standards tests were performed by safety specialists UL.
They applied a high voltage to the chargers, which were bought online from eight different countries, including the US, China, and Australia, to test for sufficient insulation.
Leon Livermore, the chief executive of Chartered Trading Standards Institute, urged shoppers to buy electrical goods only from trusted suppliers.
"It might cost a few pounds more, but counterfeit and second-hand goods are an unknown entity that could cost you your home or even your life, or the life of a loved-one," he said.
A separate operation found that of 3,019 electrical goods bought second hand, 15 per cent were non-compliant.
Officers said the unsafe electrical items, which came from charity shops, antique dealers, and second-hand shops, had failings such as counterfeit plugs and basic insulation.