Sounds like Fritz Kreisler, though generally the composers he "credited" were one or two notches down from Mozart and (J S) Bach -- Vivaldi, Boccherini, Couperin, W F Bach, Tartini, Pugnani, etc. You can find a list by going to http://en.wikipedia.org/wiki/List_of_compositions_by_Fritz_K... and searching for "falsely".
Apparently, when called on his deception he said "The name changes, the value remains".
I am reminded of a story that I am unable to locate, about a violinist who composed works and passed them off as more obscure classical music by big names (Mozart, Bach and similar). He liked composing music in the style, but he couldn't get people interested in the pieces. By passing them off as more obscure famous works from the period, people would listen to them, and respond favorably. A very similar problem, from a different perspective.
If anyone recalls the article or names, I would appreciate a link.