Tony Fadell, the man who came up with the idea for the iPod and iTunes, the combination of portable player and online store that lies behind Apple’s dominance of the digital music business, has stepped down after eight years, the US consumer technology company said.

Apple said it had appointed Mark Papermaster, an IBM chip expert, to replace him in a more narrowly defined role as head of hardware engineering for its iPod and iPhone devices division. However, the appointment was clouded by uncertainty on Tuesday, as IBM said it would seek to enforce a non-compete agreement that prevents Mr Papermaster from working for a rival for a year.