A Business Week report claims the iPhone has generated a huge grey market for unlocked units - and that insiders involved at some point in the production cycle for the machines may be involved in the burgeoning industry.

The report claims as many as one million unlocked iPhones may be in circulation across the world, with a particular heavy trade in the devices taking place in the Far East.

The news means 25 per cent of iPhone purchases have gone to users who then unlock the device for use on their chosen network, or for sale to others anxious to use iPhone.

The report also reveals that Czech firm Bladox and its Turbo SIM card may have hit a home run when it introduced a variant of its product last year which was capable of fooling an iPhone into thinking itself to be running an officially-sanctioned SIM card, even when it wasn't.

The report also explains the existence of at least one distributor who claims knwledge of a supplier with access to diagrams and repair guides that Apple would not release outside the company.

Business Week notes that Apple and its partners don't appear to have worked hard enough to end the scourge, but points out that the popularity of unlocked iPhones proves the popularity of the device, and could be good omen for when iPhone ships in as yet unsupported countries.

BusinessWeek readers report iPhone sales in Brazil, Canada, the Dominican Republic, Indonesia, Israel, Nigeria, Peru, Poland, Russia, and the United Arab Emirates.