Apple has warned that any buyer of its iPhone who has attempted to make the mobile phone work with alternative mobile networks could find the phone broken when it is next updated.
Apple signed lucrative deals with AT&T in the US and O2 in the UK so that those were the only networks in their countries to be allowed to sell the combined web browser, MP3 player and phone.
A number of individuals and companies have made fixes available which 'unlock' the phone so that it can be used on other networks. Apple now says that users of those fixes face their phones being broken the next time their handset is updated.
"Apple has discovered that many of the unauthorized iPhone unlocking programs available on the internet cause irreparable damage to the iPhone's software," said an Apple statement.
The company said that unlocking the phone "will likely result in the modified iPhone becoming permanently inoperable when a future Apple-supplied iPhone software update is installed."
The company has said that unlocking phones renders guarantees invalid. It said that though it will not deliberately attempt to break phones that have been unlocked, it will not attempt to avoid software clashes that could result in broken handsets.
Last week while launching the iPhone in the UK, Apple founder and chief executive Steve Jobs said that his company would try hard to stop consumers from using the phone on other networks.
"It's a cat-and-mouse game," said Jobs at the London launch, according to Computerworld. "We try to stay ahead. People will try to break in, and it's our job to stop them breaking in."
Users who have used unlocking software could choose not to download Apple's updates of the phone's software if they wanted to carry on using their unlocked phone.