Foster carers who smoke will be banned from looking after children under the age of five, a charity has proposed.
Children should be protected from passive smoke, the network says
The UK's leading fostering group is advising local authorities to introduce the policy on the day the English smoking ban comes into force on 1 July.
The Fostering Network has changed its advice to protect young children from smoking-related illnesses.
It also hopes to avoid any risk of legal action from children whose health is damaged by smoking while in care.
The guidelines have been produced by the network after consultation with foster carers, local authorities and agencies.
Local authorities, which have the final say over foster carers, will implement the guidance gradually, it is thought.
There are fears that the new guidance could worsen the current shortfall of foster carers which stands at 10,000 in the UK.
Chief executive of the Fostering Network, Robert Tapfield, said: "There's increasing evidence of the effect of passive smoking, and so what we have to balance is the rights of children in care to grow up in a smoke-free environment with the rights of foster parents to smoke.
"And so what our guidance will suggest is that for young children, children who will be around the home all day, it's very important that they have the opportunity to live in a smoke-free environment."
The network, which has more than 40,000 members, will also recommend that disabled children or youngsters with respiratory diseases should never be placed with a smoker at any age.
The guidance is backed by the British Association for Adoption and Fostering.