Writers must not force moral messages down children's throats in their books because it could stop them thinking for themselves, the former children's laureate Michael Morpurgo has said.

Morpurgo, the bestselling author of books including War Horse and Private Peaceful, said there was too much "propaganda" already in the world for it to be in children's books as well.

Acknowledging that his own novels have been widely praised for their anti-war stance, the author said any message must come to children naturally after they had enjoyed the story.