Britain is to make online safety lessons for children over five compulsory under a new scheme which aims to echo road safety campaigns of the past.

The lessons are part of a Click Clever Click Safe strategy which will produce guidelines for government, industry and charities on how to protect children using the web.

"The internet provides our children with a world of entertainment, opportunity and knowledge - a world literally at their fingertips," said Prime Minister Gordon Brown.

"But we must ensure that the virtual world is as safe for them as this one. We hope that "zip it, block it, flag it' will become as familiar to this generation as "stop, look, listen' did to the last".

The government says that 99 per cent of British children aged eight to 17 now have access to the internet.

However, research has shown that 18 per cent of young people had come across "harmful or inappropriate" content online, and 33 per cent of children said their parents were unaware of their web activities.

The new plans, drawn up by the UK Council for Child Internet Safety which is made up of over 140 organizations, including Google, Microsoft, and Bebo, would make online safety lessons compulsory for those over five years from September 2011.

Brown said the aim was to make advice as well-known as the "green cross code" which was designed in the 1970s to give children information about road safety

Professor Tanya Bryon, whose report last year formed the basis for the plans, said failing to tell children about online risks made them more vulnerable.