The information requested falls within the responsibility of the UK Statistics Authority. I have asked the authority to reply.
Letter from Jil Matheson, dated October 2009:
As National Statistician, I have been asked to reply to your Parliamentary Question asking how many people under the age of 18 are resident in each local authority area (295509).
Table 1 shows the number of people aged under 18 resident in each local authority area in mid-2008. These are the latest data available. A copy of the table will be available in the Libraries of the House.