London, June 18 (IANS) Children aged five must be taught about sex, a British government's health watchdog has said.

The National Institute for Clinical Excellence (NICE) is to write to every primary school asking them to start sex education when pupils are five. The recommendations include lessons on how to put a condom on and that excessive drinking can lead to sex.

It advises schools to use social networking websites to get the sex message across and calls on teachers to offer children confidential sex advice if they need it - without their parents being told.

The report also says that sex and relationships education is "more effective if it is introduced before young people first have sex".

Sex education, including information about sexually-transmitted infections, methods of contraception, pregnancy and abortion, can help children and teens delay sex until they are ready, the report said.

"It does not cause them to have sex at an earlier age, or to have more sex, or sex with more partners, and nor does it increase the number of unwanted or teenage conceptions and abortions," according to the new guidance.

NICE claimed that teaching children to "say no" could actually increase the chances of risky sexual behaviour and pregnancy.

Sex education is not compulsory in English schools and even where it is taught, parents have the right to take their children out of class. But the new guidance - albeit in draft form - will put greater pressure on headteachers to provide sex education at an earlier age, the Daily Mail reported.

The 74-page document was produced on NICE's own initiative after it convened a panel of public health officials and representatives from family planning groups to prepare guidance on reducing teenage pregnancy.

Britain's teenage pregnancy rate is the highest in western Europe. There are now more than 40,000 under-18 conceptions every year.