Former Microsoft chief Bill Gates revealed he considers letting Android become the default alternative to Apple’s iOS platform as the biggest mistake of his career.

Speaking at an event held by venture capital company Village Global, Gates said the mobile software opportunity was “a natural thing for Microsoft to win” and lamented “whatever mismanagement I engaged in that caused Microsoft not to be what Android is”.

He highlighted the winner-take-all nature of the mobile software market: “If you’re there with half as many apps or 90 per cent as many apps, you’re on your way to complete doom. There’s room for exactly one non-Apple operating system.”

By missing the boat on mobile, Gates said Microsoft lost out on a $400 billion opportunity.

“We are a leading company. If we’d gotten that one right we’d be the leading company.”

Though Gates left his post as Microsoft CEO in 2000, he stayed on as its chief software architect through to July 2008, as it fought a losing battle against Google’s Android platform for dominance.

Microsoft’s initial mobile effort, Windows Mobile, peaked in 2007 before rapidly losing market share to Android. Shortly after Gates’ departure, Microsoft revamped its mobile strategy with a new Windows Phone OS in an unsuccessful attempt to regain its footing and topple Android.