How do I set a user’s default .bashrc file?

On Ubuntu 10.4 I have edited the /etc/bash.bashrc file to set some variables like the command history size (HISTSIZE=5000), however if I create a new users Ubuntu by default gives them a .bashrc file in their home directory with this set as HISTSIZE=1000 which is overriding mine. How can I change the default .bashrc file that is created?