Former Twitter CEO Dick Costolo
Former Twitter CEO Dick Costolo says he is responsible for the growth of online abuse since 2010 Reuters

Former Twitter chief executive Dick Costolo regrets not doing more back in 2010 to stop Twitter becoming a platform used to bully and harass.

Speaking at a conference in Los Angeles, the 53-year-old said he wishes he could "turn back the clock" and stop abuse from becoming as prevalent as it is in some corners of the social network today.

Costolo says he wishes he had done more back in 2010 to curb abuse, but felt he couldn't make major changes to Twitter's direction because he was not a co-founder, having joined as chief operation officer in 2009, three years after the service was created.

At the Upfront Summit in LA, Costolo said: "I wish I could turn back the clock and go back to 2010 and stop abuse on the platform by creating a very specific bar for how to behave on the platform...I really feel like a lot of that is on me from six-seven years ago."

He added: "I wish I had done more about bullying...I mean it when I say I take responsibility for not grabbing the bull by the horns," reports Fortune.

The answer, Costolo believes, is not to block the use of certain words or phrases, but to end the 'echo chamber' which pockets of users turn Twitter into. "I think there's an opportunity to take these small clusters of people who are only talking to each other and listening to themselves in their echo chamber and find a way to engage them in rational discourse without yelling at each other on these platforms."

Costolo went on to liken social media's trolling and abuse problems to spam email, in that the solution is to make it too time-consuming and expensive for the abuser to make any gains from it.

Recognising Twitter's lengthy complaints process for users suffering from threats and harassment, Costolo said: "For too long on Twitter, if you were abused, you had to fill out this long report...that's a case where the economies are flipped in the wrong direction. I think Jack [Dorsey, CEO] and the team are working on that."

He also believes Twitter needs to work on weeding out the 'fake news' phenomenon which has spread across the internet and social media over the last 12 months.