Parents would rather their children asked them where babies come from than why the sky is blue, a poll suggested yesterday.

The survey reveals many parents dread being asked science-based questions, with nearly one in five (18 per cent) hardly ever talking to their offspring about the subject.

Just a third (32 per cent) regularly talk to their children about how science works, explaining ideas such as why steam comes out of a boiling kettle.

And the poll, which was commissioned by Shell Education Service and hosted on the Mumsnet website, reveals the science questions that leave parents stumped.

Almost one in three (29 per cent) said they would not know how to answer if their child asked “Why is the sky blue?”.

Over one in five (21 per cent) said they would struggle with “Why does the car work?”

The third most difficult question is “Why can birds fly?” chosen by 15 per cent of parents, followed by “What is water made of?” (10 per cent) and “How do fish breathe?” (nine per cent).

Just one per cent of parents said they would be stumped if asked “Where do babies come from?”, the poll found.

Almost all (99 per cent) of parents said it would help their child’s progress in science if they talked to them about the subject at home.

One in 10 (10 per cent) of the parents questioned said they do not talk to their child about science because they do not feel qualified to do so.

Shell Education Service is publishing a booklet containing easy experiments for children and parents to try at home.

Rachel Foster, associate editor of Mumsnet, said: “Some parents worry about giving the wrong answer to some of the more difficult science questions asked by their children, and as a result are avoiding discussing the subject altogether.