Facebook has reacted quickly to claims made on the Facebook Insider blog that its stratospheric growth is finally beginning to slow down.

CNBC reported this week that the social networking giant is rumoured to be planning to go public in the first quarter of next year, with an IPO valuation rumoured to be in excess of $100bn.

However, according to figures released on the Facebook Insider blog, the site lost almost 6m users in the US and 1.5m in Canada, while the UK and Russia lost around 100,000.

Not much when compared with the half a billion users the site reached in 2010, and is expected to push 700m in the very near future. But while average monthly growth for last year was around 20m, between April and May this year the site gained just 11.8m and 13.9m users respectively, said the blog, indicating a potential slowdown.

Author of the Inside Facebook blog Eric Eldon said it appeared that losses occurred in countries where the site had been active for longest. “By the time Facebook reaches around 50% of the total population in any country (depending on internet access rates in that country), growth generally slows to a halt,” he wrote.

However, the social network has responded quickly and dismissively, casting doubt on the veracity of Eldon’s numbers.

 “From time to time, we see stories about Facebook losing users in some regions,” it said in a statement, referring also to two similar posts in the last two years.

“Some of these reports use data extracted from our advertising tool, which provides broad estimates on the reach of Facebook ads and isn’t designed to be a source for tracking the overall growth of Facebook,” it added. “We are very pleased with our growth and with the way people are engaged with Facebook. More than 50% of our active users log on to Facebook in any given day.”