A new Facebook app, currently being tested by a small group of VIPs, will let celebrities monitor comments being made about them while on the go, it has been revealed.

The feature has been designed to get more famous people to use Facebook rather than Twitter. It allows them to have conversations with their fans through the site and see the comments made on their posts and photos more easily.

Katy Perry is the most followed woman on Twitter, with over 40,785,000 followers, but her Facebook page has over 56m likes, showing the potential for Facebook to overtake Twitter as the go-to social networking site for celebrities.

"We are currently testing some mobile features designed to help public figures interact with their fans," said a Facebook spokesperson told the digital news website AllThingsD.

"We are testing these features with a small group of partners and will share more details should we roll it out more widely."

The hastags and openness of Twitter make it easier for celebrities to keep tabs on their fans, but Facebook now offers its own hashtags, trending topics and celebrity pages in a bid to compete with the 140-character social network.