A competition to see who could infect an Apple computer running OS X has been scrapped by the organisers after complaints from Apple users and fears of legal action.

DVForge, which builds Apple accessories, had offered $25,000 to the first person to infect two G5 PowerMac computers running OS X 10.3 Panther connected to the internet without firewalls or antivirus protection.

The competition was organised in response to a report last week by security firm Symantec which claimed that Apple's operating system would be under increasing threat from viruses.

Jack Campbell, chief executive at DVForge, said: "I have taken the difficult decision to cancel our contest.

"I have been convinced that there may be legal issues stemming from such a contest, beyond those determined by our own legal counsel prior to announcing the contest.

"So, despite my personal distaste for what some companies have done to take advantage of virus fears among the Mac community, and my own inclination to make a bold statement in response to those fears, I have no responsible choice but to retract the contest, effective immediately."

In a personal statement Campbell described some people in the antivirus community as "fear-breeding folks preying on the lack of knowledge about how viruses work" and insisted that the virus threat is "overstated".

He also denied running the competition as a publicity stunt, maintaining that his intention was to stop people being scared of buying an Apple for security reasons.

But after the competition was launched Campbell was contacted by several security and legal experts who warned him that he was possibly committing a crime, and could actually hasten the arrival of Apple viruses.

So far no OS X virus has been detected in the wild.