Ballmer blasted the Android ecosystem as 'uncontrolled', while criticising Apple's ecosystem as being 'highly-priced and tightly controlled'.
"The ecosystem of the Android is a little bit wild, that is from an app compatibility perspective and our world perspective maybe in a way that's not always in the consumer's best interests," The Telegraph quoted Ballmer, as saying.
"Conversely the Apple ecosystem looks highly controlled, and, by the way, quite high priced," he added.
According to the paper, Ballmer launched the attack while being interviewed by LinkedIn founder Reid Hoffman at an event with "tech influencers and innovators" at the Churchill Club in Santa Clara, California.
He went on to argue that Windows Phone had an opportunity to position itself in between the two, the paper said.
"The question is how do you get the quality with maybe not the premium price of the phone, with maybe not quite as controlled an ecosystem. And how do you allow for the lower pricepoints, more affordability, diversity that comes with Android," he said.
"And I think you can say that's kind of the best of both worlds and that's available to us," he added.