Investigators have warned consumers they face potentially fatal risks after 99% of fake Apple chargers failed a basic safety test.
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.