Use the uninstaller that comes with the installation disk / image. Double click; it'll ask for your password. Uninstallation may take a while, give it a few minutes.
Can't I don't have an uninstall disk. Parallels was placed on my mac by my former employer. Is there a Mac tool to uninstall?
You could download the image from the Parallels download page. Mount it on your Mac; you'll see the uninstaller.