It started with a rogue tweet, but rumours that Google is developing its own social network to rival Facebook are gathering momentum.

Kevin Rose, who founded the social news website Digg, wrote on the microblogging site Twitter: "Ok, umm, huge rumor: Google to launch Facebook competitor very soon 'Google Me,' very credible source." It was deleted shortly after.

Adam D'Angelo, founder of the social networking site Quora, and a former senior manager at Facebook, said "This is not a rumour. This is a real project. There are a large number of people working on it." Google declined to comment.

Google has made several failed attempts to enter social networking, including Orkut and Google Buzz. It also moved to incorporate Twitter into its search results.

"They realised that Buzz wasn't enough and that they need to build a full, first-class social network. They are modelling it off of Facebook," Mr D'Angelo said.

The battle between search engines and social networks has been heating up this year. Facebook overtook Google in the US for the first time as the most popular site in March, although the data was recorded over just one week.

According to the data group Experian Hitwise, traffic to all social networks in the UK overtook search for the first time in May.

"They had assumed that Facebook's growth would slow as it grew, and that Facebook wouldn't be able to have too much leverage over them, but then it just didn't stop, and now they are really scared," Mr D'Angelo added.