Facebook's Sheryl Sandberg admits battle with Twitter and Tumblr for teenage users is getting harder

Facebook is facing it increasingly tough to fend off competition from Twitter and Tumblr in the battle for teenage users, its chief operating officer has admitted.

Sheryl Sandberg said teenagers are still using Facebook, but are also increasingly using Twitter and Tumblr.

Sheryl Sandberg told a technology conference that although the number of teenagers using Facebook is still growing, Twitter and Tumblr are becoming more and more popular with the valuable demographic.

“Teenagers are using other things more. At the same time, they continue to be very active, engaged Facebook users,” Mrs Sandberg said.

The admission is likely to fuel concerns amongst some investors that Facebook’s lifespan will be limited, and will go out of fashion in the same way that early social networks, such as MySpace and Friends reunited, have done in the past.

However, Ms Sandberg said that there was still plenty of room for Facebook to grow before the market reaches saturation point. “We are the leaders in a growing market. Do I think there’s time and room for people to do a lot more sharing before we reach the zero sum game? Yes.”

Also speaking at the event in California, Twitter’s chief executive Dick Costelo said the micro-blogging service, which allows users to post messages 140 characters at a time, can make money out of providing “the social soundtrack for TV”.