"I went to give a talk at my old school and the girls were all doing 'likes' and 'innits?' and 'it aint's', which drives me insane," she told the Radio Times. "I told them, 'Don't do it because it makes you sound stupid and you're not stupid.' There is the necessity to have two languages – one you use with your mates and the other that you need in any official capacity. Or you're going to sound like a knob."
Thompson's point about having two languages is a fair one, but to write off a few slang terms as making you sound "stupid" seems to me to be a step or two too far. Fair enough, if you don't like those expressions, then you've got a right to say so, but to equate slang with stupidity is just narrow-minded. To make matters worse, Thompson then slips into her own generation's slang when she says that saying "like" and "innit" makes you "sound like a knob".
Why is it OK for Emma Thompson to mix her codes in the pages of a national publication, while it's apparently not OK for teenagers at her old school to switch codes? Sounds to me like the old prescriptivist stance that younger people's use of language is a degraded form: a crumbling castle idea, that Jean Aitchison effectively nails in her famous Reith Lectures.
The Independent has a good leader article on the story, which you can find here.