Apple''s chief of security operations has left the company just months after the world's largest technology company faced criticism over the tracking down of what has been widely reported as a missing prototype of an iPhone, according to Reuters.

The consumer device giant's vice-president of global security, John Theriault, has retired, a person close to Apple said. Apple declined to comment.

Apple's security team was criticised after two of its members entered a house in San Francisco in the summer to search for a "lost item", thought to be a prototype of what eventually became the iPhone 4S.

The company's security staff were accompanied by San Francisco police, who said they did not enter the residence. The police said Apple had tracked the lost item to the house.

Apple did not find the item, but the company faced a backlash on the internet and media after 22-year-old Sergio Calderon came forward to say he had let the security staff in, thinking they were police officers.

An attorney for Mr Calderon, David Monroe, said in the US on Friday that his client was in settlement negotiations with Apple and declined to comment further.

Mr Theriault joined Apple after a stint as chief of security at Pfizer, according to his LinkedIn profile. Before that, he was a special agent in the Federal Bureau of Investigation.

In 2010, Apple faced similar criticism when investigators raided a technology journalist's home to retrieve an iPhone prototype. The prototype, left by an Apple employee in a bar, had been sold to tech blog Gizmodo.