Keeping windows open and improving ventilation in schools is much more effective at reducing coronavirus transmission than asking young children to wear face masks, a Government scientific adviser has said.

Professor Calum Semple, a member of the Scientific Advisory Group for Emergencies (Sage), told BBC Radio 4’s Today programme that he is “not a fan” of asking young children to wear masks, and there are better strategies for managing the virus.

It came after some schools, including Selsdon Primary School in Croydon, south London, said pupils must wear face coverings at all times, except during sports lessons or when eating or drinking.

A statement from the school said: “This decision was solely based on keeping our staff, pupils and their families safe in the current situation.”

But the Department for Education said primary school children should not be asked to wear masks.

Prof Semple, speaking in a personal capacity, said: “Primary school children are the lowest risk both to themselves and to society.

“There is really good data coming out … that shows that children are half as likely to acquire the virus to a third as likely to acquire the virus.

“When it comes to transmitting, they are probably half as likely to transmit it as adults.

“That risk actually gets smaller as you go into younger age groups.

“So I am not a great fan of young children wearing face masks.”

He said he agrees that young children will find it difficult to wear the masks properly.

He added: “If I had to invest in a single activity to improve the environment both for the children and the adults, I’d be looking at improving the ventilation, unsealing windows that have been painted shut and kept shut for energy-saving reasons … improving air exchanges.

“That would be a much more effective way to reduce transmission in schools.”

Asked about the risk to teachers, Prof Semple said the data shows that teachers going to school “as a workplace are no more at risk than people in general society going about their daily living and normal working environment”.

A Department for Education spokesman said: “Children in primary schools should not be asked to wear face coverings when they return to school from  March 8.

“Our guidance is clear – face coverings are only necessary for pupils in year 7 and above.”