iPhone (4)

Carl Icahn, the billionaire activist investor, has sold his entire stake in Apple after the company revealed falling sales of its iPhone for the first time.

Mr Icahn - who earned himself the 'activist investor' title by frequently urging changes at the companies he holds shares in - made a reported profit of around $2 billion on his shares, which were last year valued at around $6.5bn. He owned 53 million shares in the tech giant.

Earlier this week, Apple saw its revenues fall for the first time since 2003. Mr Icahn cited concerns over the company's growth in China as a key reason in his decision to sell his stake. China had been a source of huge growth over the past few years as it expanded its business there. But the company reported a 26% in iPhone sales during the first quarter, as it came under increasing pressure from cheaper Chinese smartphones.

In March, Apple was forced to removed its iBooks and iTunes movies services from China after the government passed a law requiring any content available to the Chinese public to be stored on serves in China. Apple said it was hoping to offer the service in China again soon.

Speaking to US TV network CNBC, the activist investor said he spoke with Apple chief executive Tim Cook to explain his decision.

"I called him this morning to tell him that [he was selling his shares], and he was a little sorry, obviously. But I told him it's a great company," Mr Icahn said.