Caroline Criado Perez said it was "great" that Twitter had taken a "first step" in dealing with harassment on the social media site, but said more needed to be done.
Ms Criado Perez, from north London, was one of a number of women who were subjected to a torrent of abuse by Twitter users last month.
Ms Criado Perez said: "It's great that Twitter has listened.
"There are still issues: users have to agree for the report to be potentially shared with the harasser, and there are some boxes that could be auto-populated that aren't. But overall, this is a fantastic first step."