Kids Caring for Other Kids

There has been a bit of a stir caused in the UK right now because a mother was given a caution for leaving her 14 year old looking after her toddler for 30 minutes.

How old do you think kids need to be to care for younger siblings?

Was the 14 year old acting irresponsibly, or was it just the fact that the sitter was 14? How old does the UK want kids to be before they are allowed to babysit? I know of responsible 12 and 13 year olds who babysit for unrelated kids here in the US, and even younger ones who care for siblings.

The mother was only gone for half an hour, the fourteen year old was fine with the child-there was no problems for either, and it was only discovered then the teen mentioned it to a neighbour-who promptly reported it.