The commericial (pictured), which looked official and appeared on Facebook and Twitter, told Apple users the new iOS7 software would make their phones waterproof.

Displaying an iPad and an iPhone 5S covered in water droplets, it read: “A smart-switch will shut off the phone’s power supply and corresponding components to prevent and damage to your iPhone’s delicate circuitry.”

At the bottom of the poster was a promise that “waterproofing [is] covered by Apple’s warranty policy”.

Angry replies followed the circulation of the fake advert on Twitter – after followers had tested the theory.

One user wrote: “Whoever said iOS 7 was waterproof **** you.”

Another tweeted: “OK whoever said iOS 7 is waterproof GO **** YOURSELF.”

The Telegraph said the prank started by controversial forum 4Chan which has a chequered history of hosting faked material.

Apple, which is yet to comment on the fake advert, said more than 200 million of its smartphones and tablets are now running the redesigned operating system iOS 7, “making it the fastest software upgrade in history.”

Apple began worldwide sales Friday of the high-end iPhone 5S and a lower-cost iPhone 5C, drawing crowds from Australia to Tokyo to Paris to New York.