Facebook now has more than a billion users who access the site at least once a month, a milestone its founder Mark Zuckerberg hailed as the proudest achievement of his life.

The social network has seen user numbers plateau in Britain and America but still managed to add 100m active members since April as it gained popularity in developing countries.

It is the first social network to hit the billion-member threshold, and has twice the users of its nearest competitor, the microblogging site Twitter.

However, the milestone had little impact on Facebook’s ailing share price. The social network has struggled to regain its footing after its disastrous $104bn (£64bn) flotation in May, and yesterday saw its shares edge up just 10 cents to $21.93 – little over half their value at Facebook’s initial public offering.

Mr Zuckerberg, who founded the company in 2004 from his Harvard University dorm room, said: “Helping a billion people connect is amazing, humbling and by far the thing I am most proud of in my life”. He added that his ultimate goal is to have the world’s entire population of nearly 7bn people on the social network.