Is spanking illegal in the UK?

I'm not bringing this up in order to have a debate (although it may be interesting if people remain calm)... I just wanted to know: is spanking illegal in the UK? I think I remember reading somewhere that it was.

I can understand why you are a bit confused. As I understand it, it's not illegal to smack, but it is illegal to cause injuries that might arise from severe smacking - bruising etc.  This is the latest I could find about it:

http://www.nspcc.org.uk/html/home/newsandcampaigns/physicalpunishmentmediabriefing.htm