Twitter's CEO signs off with a warning: 'regulation is a threat to free speech'

Twitter CEO Dick Costolo warned that government regulations of social media will muzzle free speech, during a farewell interview published on his last day on the job.

Costolo, who is ending a five-year stint as Twitter CEO, told The Guardian that regulation is a "threat" to free speech.

"I can't think of an example where regulation didn't have unintended consequences, and I'm unable to conceive of a regulatory body that will be swift enough to deal with the constantly evolving issues of ethics, communication and technology. I just don't think it's possible."

The comments are in-line with Twitter's longstanding stance as a champion of free speech - company executives once referred to Twitter as the free-speech wing of the free-speech party. Lately, the company has been criticized for failing to crack down on online bullying and abuse that occur on its service, as well as for providing a platform for violent extremists.

Costolo said the company has tripled the size of the internal team that stops abusive language on the service, and has made it tougher for people with blocked accounts to open new accounts.

Still, he told The Guardian that social media services like Twitter should not be regulated the same way as other communication services such as television broadcasters.

Twitter co-founder Jack Dorsey will take over as CEO on an interim basis until the board finds a permanent successor. Costolo helped grow Twitter from a small, privately held startup to a publicly listed company with 300 million users. But the company has come under fire for disappointing growth and financial performance.

The next CEO will have to deal with speech and global political issues as much as technology, Costolo said.

"When I took on the role of CEO I thought of myself as a technologist, but I've had to become more and more concerned with the geopolitical landscape, as have all my counterparts in tech," he said.