The information requested falls within the responsibility of the UK Statistics Authority. I have asked the authority to reply.
Letter from Glen Watson, Director General for ONS, to Lord Lea, dated January 2013.
As Director General for the Office for National Statistics, I have been asked to reply to your Parliamentary Question asking for the estimate of the number of people in the United Kingdom whose usual working hours are between midnight and 8.00 am. (HL4479)
Estimates of people working specific hours are not available. However, the Labour Force Survey (LFS) provides estimates of people working particular shifts. Of the reported working patterns available the most appropriate for this question is night shift workers. Night shift workers are people working permanent night shifts, typically between the hours of 18:00 to 06:00, thus working past midnight into early morning. This does not include people who occasionally work night shifts.
For the period April-June 2012, which is the only quarter that asks this question annually, it is estimated that 361,000 people in the UK worked permanent night shifts.
As with any sample survey, estimates from the LFS are subject to a margin of uncertainty. It is estimated that the true value is likely to lie between 326,000 and 397,000.