Re-walpapering

Hey guys,



So i've got some ghastly green wallpaper in my place that is started to flake away in some places. I'm just wondering, do i need to remove the entire wallpaper before applying new wallpaper, or can i just remove the flaky bits where possible and then just wallpaper over the top? I'm just trying to save myself as much time and effort as i can! :)



Thanks!