There is not a option to manually add a member in the control panel.
there are ways to get around this issue but it may present problems down the road for things such as lost password and watched items notification.
But anyway I assume you have email verification and Unique emails per account enabled in the cp>>Registration settings.
So just register the user the normal way and enter a completely bogus email address. Then the user will show in the registration queue in the control panel. Then you can approve them even though the email is not verified.
This part I am not sure about.
Edit the new user in cp>>Member management and try adding the legit duplicate email address.
