Consumers are being warned off buying bargain iPhone chargers online after 99 per cent failed a basic safety test.
Out off 400 counterfeit Apple chargers from online suppliers around the world and found that 397 of them failed a basic safety test, according to safety campaigners.
Knock-off cables can be bought for as little as 1p on auction sites such as eBay while Apple's official leads retail at £19.
Common problems with fakes included counterfeit plugs, non-sleeved plugs where the metal pins are exposed, live parts, two pin plugs attached and only basic insulation.
They could also cause potentially fatal electric shocks.
The Chartered Trading Standards Institute issued the warning during National Consumer Week, urging shoppers to check goods' safety and authenticity before they buy.
A second operation targeted local charity shops, antique dealers and second-hand shops and found 15 per cent of 3,019 used electrical goods were non-compliant, rising to 27 per cent in London.
Leon Livermore, Chartered Trading Standards Institute chief executive, said: "Only buy second-hand electrical goods that have been tested and only buy online electrical goods 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."
Extra guidance issued includes not over charging electricals and disconnecting them once they are charged, not covering devices while plugged-in, and not using damaged or frayed cables.
Lord Toby Harris, chair of National Trading Standards, said: "Many of us quite rightly assume that everything we buy will be safe, but recent work by our teams show how dangerous electrical goods can easily end up in homes up and down the country.
"Criminals across the globe are using online platforms to lure you in with cheap deals for fake items, many of which are dangerous and have been known to overheat and cause house fires.
"Protecting consumers from harm is our top priority and National Trading Standards teams are working closely with partners - including search engines, social media platforms and producers - to remove dangerous electrical items from our supply chain.
"Our teams help prevent dangerous goods from entering the country, undertake enforcement work to remove criminal social media profiles and seize hordes of dangerous items destined for households across the country.
"Sadly, we suspect our work is just skimming the surface and we urge consumers to be vigilant when buying electrical products online: be wary of deals that look too good to be true and search for reviews of the seller before making your purchase.
Gillian Guy, chief executive of Citizens Advice, added: "Counterfeit electrical goods are likely to be poor quality and in the worst cases unsafe.
"Look out for tell-tale signs of counterfeiting such as mistakes in brand names or logos, and check plugs for safety marks - all genuine electrical items made in the EU should have a CE mark on them."
Baroness Lucy Neville-Rolfe, minister of state for energy and intellectual property at the Department for Business, Energy and Industrial Strategy, said: "I am delighted to support the National Consumer Week campaign which this year highlights unsafe and counterfeit electrical products.
"The Government is committed to promoting consumer awareness of the dangers of buying counterfeit goods and encouraging consumers to choose legitimate goods and services, which helps honest traders.
"We will continue working closely with our partners to build respect for IP in line with our enforcement strategy published earlier this year."