This article is from the alt.comp.lang.learn.c-c++ Frequently Asked Questions. Compiled by Sunil Rao firstname.lastname@example.org.
According to a number of C++ experts, including its creator Bjarne Stroustrup, and Marshall Cline (the author of the C++ FAQ), the answer is a firm no.
Look up the C++ FAQ to see why Cline thinks you do not need to learn C before C++. A post by Bjarne Stroustrup to comp.lang.c++ addresses this point too. http://www.research.att.com/~bs/learn.html
"Learning Standard C++ as a New Language" - a paper by Stroustrup available from http://www.research.att.com/~bs/papers.html - examines this much-debated issue in great depth, but the paper is aimed more at educators than at beginners.