FormsAuthentication Redirection Login page

I am using Forms Authentication in my ASP.NET MVC Web Application and we are noticing that when the Forms Authentication Cookie times out, rather than redirecting the entire window back to the Login page, the Login page is being loaded in the current target dialog or current pane of the navigation.

Instead, we want the Login page to completely replace whatever existing page content is there (removing all navigation elements etc.) and simply display the Login page by itself.

Is there a recommended method to accomplish this?

If so, what code can I use to do this and where do I need to put it?

Thanks