Facebook has started rolling out a paid messaging service in UK, charging users from a low 71p to as much as £11 to send messages to people outside their circle of friends. The highest rate is afforded when touching base with celebrities, depending on how famous they are.

An unidentified spokeswoman for Facebook also noted the fee was also dependent on the person's country location and whether they have already received paid messages recently.

The trial paid messaging service was being tested among a very small percentage of users.

Asked how long the trial goes, the spokeswoman did not confirm any specific timeframe.

"There is no set timescale. It depends on what happens, what feedback we get as to whether it is rolled out nationally. We are testing a number of price points in the UK and other countries to establish the optimal fee that signals importance. This is still a test and these prices are not set in stone."

The prices could run from only 71p ($A1.04) to contact Prince Harry's girlfriend, Cressida Bonas to £10.68 ($A15.67) to contact Tom Daley, British Olympic diver, over Facebook. Facebook uses a secret "fame" algorithm to determine a celebrity's fame prowess.

It is still not clear if Facebook will extend the trial paid messaging service to Australia, which has 11.36 million users, according to a November report by the Australian Communications and Media Authority.

The Facebook spokeswoman the system was being introduced to avert the proliferation of spam in the system.

"Our aim was to find a way to do this that didn't become a vehicle for spam. To do this we began testing a system of paid messages. The rationale is that applying a small fee will dissuade people from sending spam messages and ensure that these are genuinely important," she said.

"This just gives people another option to contact non-friends and ensure the message goes into their main inbox, rather than the 'Other' folder which people don't check as often. The test doesn't change or prevent anything you can already do; it's just an optional extra."

Facebook started the paid messaging service system in the US in December 2012, and extended to 36 other countries, on at least ten per cent of users in each country. Users will be prompted to enter payment details if they will avail the service.