The office of the Data Protection Commissioner is to begin an audit of Facebook following a series of complaints about the social networking site.

The office will examine all of Facebook’s activities outside the US and Canada and any decision it makes could have implications for millions of global users.

The Commissioner says it is likely to be the most detailed, challenging and intensive audit ever undertaken by his office.

Around 800 million people across the globe have profiles on Facebook.

Its European Headquarters in Dublin are responsible for all users outside the US and Canada.

A group called Europe Versus Facebook has taken 22 complaints about the way the website retains user information to the Data Protection Commissioner here.

Among its complaints are that the "Like" button creates data that can be used to track users all over the internet; that tags can be applied without the consent of the user and pokes, posts, pictures and messages can still be seen after they are deleted.

Observers say that the outcome of the investigation will be watched closely internationally, particularly among larger digital companies who are located in Ireland or are looking to locate here.

The Data Protection Commissioner is due to publish his findings by the end of the year.