Facebook has lost millions of users per month in its biggest markets, independent data suggests, as alternative social networks draw the attention of those seeking fresh online playgrounds. As Facebook prepares to update investors on its performance in the first three months of the year, with analysts forecasting a revenue rise of 36 per cent from last year, studies suggest that its expansion in the United States, Britain and other major European countries has peaked. In the last month, the world's largest social network has lost six million US visitors, a four per cent fall, says analysis firm SocialBakers. In Britain, 1.4 million fewer users checked in last month, a fall of 4.5 per cent. The declines are sustained. In the last six months, Facebook has lost nearly nine million monthly visitors in the US and two million in Britain. Users are also switching off in Canada, Spain, France, Germany and Japan, where Facebook has some of its biggest followings. A Facebook spokeswoman declined to comment. "The problem is that, in the US and UK, most people who want to sign up for Facebook have already done it," said new media specialist Ian Maude at Enders Analysis. "There is a boredom factor where people like to try something new. Is Facebook going to go the way of Myspace? The risk is relatively small, but that is not to say it isn't there." Alternative social networks such as Instagram, the photo sharing site that won 30 million users in 18 months before Facebook acquired it a year ago, have seen surges in popularity with younger age groups. Path, the mobile phone-based social network founded by former Facebook employee Dave Morin, which restricts its users to 150 friends, is gaining a million users a week and has recently topped nine million, with 500,000 Venezuelans downloading the software application in a single weekend. Facebook is still growing fast in South America: monthly visitors in Brazil rose six per cent in the last month to 70 million, says SocialBakers, whose information is used by Facebook advertisers, while India has seen a 4 per cent rise to 64 million - still a fraction of the country's population, leaving room for further growth. But in developed markets, other trackers are reporting declines. Analysts at Jefferies bank have developed an algorithm that interfaces directly with Facebook software and it "suggests user levels in [the first quarter] may have declined from peak", according to a recent note. Jefferies saw global visitor numbers peak at 1.05 billion a month in January, before falling by 20 million in February. Numbers rose again this month. The network has now lost nearly two million visitors in Britain since December, says research firm Nielsen, with its 27 million total flat on a year ago. The number of minutes that Americans spend on Facebook seems to be falling, too. The average was 121 minutes in December last year, but that fell to 115 minutes in February, according to comScore. As Facebook itself has warned, the time spent on its pages from those sitting in front of personal computers is declining rapidly because we are switching our screen time to smartphones and tablets. Wary of competition from services that were invented for the mobile phone rather than computers, Facebook founder Mark Zuckerberg has driven through new initiatives in the last year designed to appeal to smartphone users. The most significant is the Facebook Home software for use on certain Android phones.