I want to export a wordpress site with themes and images to html format like we can do in blogspot. Is there a plugin or a tool for the same.
Probably http://www.HTTrack.com/ is the right tool for you: It is an easy-to-use offline browser utility and allows you to download websites "to a local directory, building recursively all directories, getting HTML, images, and other files from the server to your computer".
The WP Static HTML Output plugin will do this.
Just use a website scraper to do this.