The inventors of a new internet scanning device say that a PC registered to the Holy See was used to alter facts about the Sinn Fein president on Wikipedia.

They claim links to a newspaper article about a double murder in 1971 were removed. These links made reference to Gerry Adams.

But a Sinn Fein spokesman said it was difficult to determine the authenticity of the argument. "They could come from technology manufacturers," he said.

In a statement the spokesman said the revelations raised a bigger issue. " The ability and the tool to trace activity on the internet are vital in the battle against child pornography and paedophilia. It is crucial that law enforcement agencies are able to accurately identify all internet users in the battle against these activities," he said.

A notice on the Wikipedia website on Gerry Adams today read: "This page is currently protected from editing until August 17, 2007 (UTC) or until disputes have been resolved. Protection is not an endorsement of the current version. The neutrality of this article is disputed."

Wikipedia is a popular free online encyclopaedia which can be developed by anyone.

The scanner device designed to detect spelling mistakes and factual errors can be used to trace users' unique identification - known as an 'ip' address.

Computer expert Dr Kevin Curran told the BBC: "It is interesting because people do forget when they go online they can be traced."

It is not known how many people had access to the Vatican computer system.

However, Dr Curran said it was difficult to determine if the person was an employee or if they had maliciously hacked into the Vatican system and were " spoofing" the 'ip' address.

Scanner inventor Virgil Griffith said: "Technically, we don't know whether it came from an agent of that company; however, we do know that edit came from someone with access to their network."