Cameron pledges retribution on sales firms exploiting children

The ban is one of a range of measures planned by the Tories to halt the excessive commercialisation and sexualisation of childhood by advertisers and marketeers.

New powers would also be introduced to outlaw "peer-to-peer" marketing techniques aimed at children, such as viral film clips carrying advertising messages which are shared on mobile phones and the internet and the recruitment of children as "brand ambassadors" to promote products on social networking sites.

Mr Cameron highlighted research indicating that children – particularly those from deprived backgrounds – are increasingly influenced by marketing messages encouraging them to buy expensive branded products, including clothing and games.

The Tory leader said he wanted to make Britain "the most family-friendly country in the world", and a key part of that would be "making sure that business is responsible in how it markets and advertises products to children".

Mr Cameron revealed he had told his own six-year-old daughter Nancy to stop listening to songs by Lily Allen because some of the sexual references in her lyrics were inappropriate for a child of that age – and Nancy once broke his iPod in a "tussle" with wife Samantha over whether she could listen to Allen's music.

He confirmed he turned down an invitation to appear on Piers Morgan's ITV1 interview show because he felt the format was not "substantial" enough.

He added that his wife would carry on with her professional work if he became prime minister. Mrs Cameron is creative director of up-market stationers Smythsons.