Facebook is trialling a paid system for private messaging on its website.

The social network has started testing a method of charging users to send private messages to strangers. The system uses a sliding scale of fees based on the number of followers they have and how many users are paying to contact them, according The Telegraph.

Previously, messaging a user you are not friends with on the site was free but Facebook insists the new method is designed to prevent spam messages. Messages used to arrive to a user's inbox but now they are filed in an 'other' box.

Facebook said in a statement. "The system of paying to message non-friends in their inbox is designed to prevent spam while acknowledging that sometimes you might want to hear from people outside your immediate social circle,"

Last year, Facebook tried out a system where an over-18 user could pay $1 to send a message to a stranger with an alert making it more likely to be read.

"We are testing a number of price points in the UK and other countries to establish the optimal fee that signals importance."

The sliding scale means users can message another regular Facebook member for a small amount but contacting a celebrity will cost considerably more – a new addition to the system. For example, a message to Olympic diver Tom Daley would set you back £10.68. Alternatively, tweet them on Twitter for free.

Last week Facebook announced its Facebook Home app for Android which takes over most of the operating system. The HTC First, aka the Facebook Phone, will be the first to come pre-loaded with it.