Dr Sarah Jarvis. I've heard her say it a few times but the latest was this morning on the Jeremy Vine show.
Just make sure you understood me correctly. She isn't saying that children that age don't pass it on. Just that there is no evidence yet to confirm that they do pass it on. I haven't actually seen what he said, but I guess from news clips I've seen that he isn't keen on children returning to school. So it's possible he may have said something like "there's no evidence to suggest that children that age don't pass the virus on". Which is a different way of saying the same thing, just from a different standpoint perspective.
Sarah Jarvis is a bit of a smarmy smart ass actually, so if you can prove she was wrong I wouldn't take it too much to heart