A lad of 12 who tried out the new iPhone 4S in Tesco was stunned when it told him: "Shut the f*** up, you ugly t***."
The phone's Siri system, which answers spoken questions, came back with the foul-mouthed insult when Charlie Le Quesne asked: "How many people are there in the world?"
Charlie's horrified mum Kim said: "The phone was a demo version and was low enough on the shelf for Charlie to have a go with it. He asked it a simple question and we couldn't believe the filth it came out with.
"I thought I must be hearing things. So we asked again and the same four-letter stuff blared out.
"I asked for the manager and after staff heard it they agreed to unplug it."
Apologetic staff at Tesco in Coventry told Kim pranksters had tampered with the phone's set-up instructions.