In a move which, according to Facebook, is aimed at stopping the users of the popular social networking from sending unsolicited messages to celebrities and people they are not friends with, Facebook users in the UK are now being charged up to £10 for sending messages to other users outside their circle of friends.

Under the scheme being tested in the UK, a standard message to non-friends on the social network costs now costs 71p in the UK; though the `free' communication of Facebook users with their friends and people with whom they share mutual friends remains unaffected by the trial scheme.

The charges for messages to non-friends will vary, depending upon the popularity of the recipient. For example, £10.68 is the maximum cost for sending a message to celebrities like Olympic diver Tom Daley; and the message fee for contacting US rapper Snoop Dogg is £10.08.

The fee for sending messages to non-friends can be paid online by the users instantly with a credit or debit card, though the under-18 users - who are blocked from receiving unsolicited messages - are barred from doing so.

About testing "the system of paying to message non-friends in their inbox" in the UK, Facebook said in a statement that the move will help "prevent spam;" and added: "We are testing a number of price points in the UK and other countries to establish the optimal fee that signals importance."