Twitter co-founder Evan Williams is to step aside as CEO of the social networking site in order to concentrate on making it more profitable.

Despite growing subscribers to an estimated 160m worldwide, Williams says Twitter isn't reaching its potential as a profitable company.

He says on the company blog: "Growing big is not success in itself.

"Success to us means meeting our potential as a profitable company that can retain its culture and user focus while having a positive impact on the world. This is no small task."

Cash for tweets

Willams will hand over the reigns to current COO Dick Costolo, so he can "focus completely on project strategy."

Despite Twitter becoming a pop-culture phenomenon in the last couple of years, it is renowned for its inability to effectively monetise its huge traffic stream.

In April this year the company introduced a sponsored tweets scheme in order to bolster the coffers, but with Facebook's Mark Zuckerberg now worth a reported $6.9 billion (£4.3 billion), there's a long way to go for Williams in his new role.

Williams became CEO in 2008 after the board of directors decided he was better equipped to handle the role than his co-founder Jack Dorsey.