British actress Emma Thompson is convinced social media is dangerous and will have disastrous consequences for youngsters who grow up obsessed with the Internet.

The Harry Potter star is adamant she will never sign up for websites such as Twitter or Facebook as she fears there are hidden dangers for users who post intimate details online.

She tells America's Vanity Fair magazine, "I'd rather have root canal (dental) treatment for the rest of my life than join Twitter... I can't bear the thought of being connected all the time. God knows what it's all doing to us... In about 25 years time, maybe, a sudden generation will just drop dead. Everyone will just die on the same day. And I'll say, 'Oh, what do these people have in common? Hang on.They were connected every day 24/7, you know!... Then we will wonder why, at the age of 60, an entire generation chucks itself off a cliff like a bunch of lemmings. Actually, that's the most likely outcome, don't you think? It's like, 'I can't take this anymore!' It's the lemming generation, I'm telling you."