Will I be able to get a malicious account removed?

This has been going on for more than three years. A person was harassing me on Twitter to the point where I deleted my account. Unfortunately, this person proceeded to waut until my former username became available and set up a new account in the same name that I used - that of a pet. I periodically get messages from friends who have been interacting with this account under the impression that it was me, but realised that it wasn't me when they noticed that the account was saying some pretty nasty things about me. Have I got any grounds to report the account and get it removed? Should add that the username has my first name in it, giving people more reason to believe that it's me.

Grateful for any help.