Smoking ban in cars unenforceable?

Nick Clegg has said he opposes as illiberal plans for a law banning smoking in cars when children are present. He said smoking in such circumstances was irresponsible but he did not see how a law could be enforced. MPs are expected to be given a free vote on the measure, after peers voted on Wednesday to back a ban being inserted into the children's bill. Speaking on LBC's Call Clegg programme on Thursday, the deputy prime minister said:
"I know the temptation is always to say there is a problem, where is the law? I am quite an old-fashioned liberal. I don't think you should legislate unless you think it is going to make a difference. I don't see how this is going to be enforced so families speeding along the M4 and mum or dad is smoking, how on earth are you going to properly enforce it?"

Smoking ban in cars with children unenforceable, says Nick Clegg The Guardian 30 January 2014