Double Tapped Breaker

hello all,
at a recent home inspection, the inspector noted that a breaker was double tapped and this is not good because it could arc, one wire is for lights and the other is for the doorbell transformer, he mention i could use a 2 pole breaker like the one pictured here, is this true or safe?? what else could i do with the doorbell wire? put it on another seperate appropriate breaker?
http://www.drillspot.com/pimages/1565/156513_300.jpghttp://www.drillspot.com/pimages/1565/156513_300.jpg