This is one of those stupid ideas that circulate within our trade. See my thread " Myths of the Trade" I think this one is in there. Some of these local council COWs are right berks TBH. This misconception was around in days of the 14th Ed. , a lack of understanding of the Reg. that said "Only the live conductor can be switched with a single pole switch, not the neutral" .It's in big bold letters in the spec mate. NO NEUTRAL CONDUCTORS TO BE TAKEN TO SWITCH BOXES
Or something to that effect, it's deffo there though.
You get this from people who have never actually done the job .