iCloud backup

I have just got a new iPhone 5. I used to have an iPhone 4 and used iCloud to transfer all the data over to my new phone.

I have now restored my old iphone 4 ready to sell but my new iPhone 5 will now not back up in iCloud as it says there is not enough space but my old phones back up is still appearing I'm iCloud.

My question is can I delete my old phones backup or will it remove all the data transferred over ony new phone ?