Almost 100 per cent of fake Apple chargers have been deemed dangerous after failing safety tests by UK investigators.

Trading Standards, which commissioned the tests, had 400 fake Apple-branded chargers put through their paces only to find that just three were safe enough to protect against electric shocks.

The chargers were purchased online from eight different countries, including the US, China, Colombia, Thailand and Australia and were treated to high voltages by safety specialists UL to test for sufficient insulation that prevents electric shocks.

The 99 per cent fail rate was shocking and showed the importance of buying genuine goods from trusted suppliers, particularly when purchasing over the internet, said Leon Livermore, chief executive of Chartered Trading Standards Institute.

"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."

The Trading Standards warning over fake Apple chargers follows news in October that an Apple investigation found almost 90 per cent of Apple-branded iPhone chargers and accessories on e-commerce platform Amazon were fakes. The tech giant is in the process of suing distributor Mobile Star for allegedly selling the counterfeit products on Amazon. The counterfeits posed a danger to consumer safety, including overheating, causing electric shocks and catching fire, Apple said.

Mobile Star is not implicated in the Trading Standards tests.

Meanwhile, a separate investigation by Trading Standards found 15 per cent of more than 3,000 second-hand electrical goods, bought from charity shops, antique dealers and second-hand stores, were not safety compliant and had counterfeit features, such as plugs. In London, the non-compliant figure was 27 per cent.

Lord Toby Harris, chair of National Trading Standards, said the operation showed how dangerous counterfeit electrical goods can easily end up in homes. "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."

He said National Trading Standards was working with search engines, social media platforms and producers to remove fake electrical items from the supply chain by removing criminal social media profiles and making seizures. Already, more than 9,500 suspicious online selling platforms have been removed as part of National Trading Standards' Operation Jasper.

However, he added: "Sadly, we suspect our work is just skimming the surface and we urge consumers to be vigilant when buying electrical products online."

In the lead up to Christmas, Trading Standards is emphasising the risk of fake electrical goods, with the warnings coming at the close of National Consumer Week.

Baroness Lucy Neville-Rolfe, minister of state for energy and intellectual property at the UK's Department for Business, Energy and Industrial Strategy, said: "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 out partners to build respect for IP in line with our enforcement strategy published earlier this year."