Google has admitted that some users of its Google Docs online word processing service may have had their documents shared with unauthorised users.

A flaw in the system meant that the documents of some users were marked down as collaborative items, allowing third parties signed up to the system to access and amend them. The company has since claimed that the flaw has now been fixed.

"We've identified and fixed a bug where a very small percentage of users shared some of their documents inadvertently," said the company in a blog posting.

"The inadvertent sharing was limited to people with whom the document owner, or a collaborator with sharing rights, had previously shared a document."

The flaw did not affect all Google Docs applications. Text documents and presentations could be accessed by others, but spreadsheets could not. Google is contacting everyone who was hit by the problem.

The company claimed that just 0.5 per cent of its customers were affected, and that "a specific sequence of user actions" would have been necessary for unauthorised users to access the documents.