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

Breath tests to target smoking in pregnancy

Pregnant women should be tested to see if they are smoking, and if they are they should be helped to quit, according to the body which issues guidance to the NHS. The National Institute for Health and Clinical Excellence (Nice) says midwives should give carbon monoxide tests to all women they see at antenatal appointments. An estimated 21% of women smoke during pregnancy. This harms foetal growth and development, with smokers three times more likely to have a baby with low birth weight — a leading cause of infant death.
Pregnant mothers to be tested to see if they are smoking, under new NHS guidance - The Independent 12 May 2013