Facebook and other social networking sites would have to advertise the 999 emergency number on their pages under new Government guidelines to improve the safety of children online.
A copy of the draft guidance, obtained by the Telegraph, shows that the Home Office wants sites like Bebo and MySpace to display adverts for the emergency services to encourage children to call the police directly if they think they are being
targeted by people who might be trying to abuse them.
It also suggests sites should take steps to make it more difficult for children to lie about their age and gain access to sites aimed at older users.
These could include offering free software which parents could download to enable them to restrict the websites children visit and the amount of time they spend on them.
In the first report by the Home Office into social networking sites, a powerful coalition of experts warn that children are at risk of online bullying, sexual "grooming" by paedophiles and online fraud.
Jacqui Smith, the Home Secretary, will publish the 73-page document on Friday, which also warns parents about anorexic websites which encourage teenage girls to compete to lose weight, and sites which promote self-harm and suicide.
It is understood that sites will be urged to set the default privacy settings of under-18s to "private" to prevent strangers accessing their profile pages. Currently, the default settings on many social networking sites are
"open", allowing personal information to be shared with all users.
Most children and young people use the internet positively but sometimes behave in ways that may place them at risk, says the document, which has been drawn up by the Home Office's taskforce on online child protection in consultation with
websites, mobile phone operators, children's charities, parent groups and academics.
Young people may also engage in behaviour that is risky to themselves including cyber-flirting and cyber-sex. These situations can quickly escalate to a point where they may lose control.
Parents will be issued with an eight-point guide on how to ensure that their children use social networking sites safely. They will be urged to discuss with their offspring the dangers of flirting online and meeting strangers they have
encountered on the internet. They will also be encouraged to contact the police immediately if they suspect that their children are being "groomed" by online predators.
Millions of children are using social networking websites intended for older users, according to a study by the media regulator, Ofcom.
Research into internet use has found that, among children with internet access, more than a quarter of eight to 11-year-olds claimed to have a profile page on a social networking website. This is despite nominal age restrictions aimed at
preventing pre-teens from using such sites.
MySpace, owned by Rupert Murdoch's News Corporation, says its users should be at least 14 to register, while Facebook and Bebo claim an age limit of 13.
The study, commissioned by the regulator's media literacy unit, surveyed more than 7,000 adults and children around the UK.
It outlined a disparity between the perception of social networking among adults and children. While 65% of parents said they set rules for the way their children used social networking sites, only half of children said their families had laid
down restrictions. A further 43% said their parents placed no limits on what they could use sites for.
The use of the internet by children is something of a hot political topic at the moment. As well as the Byron review, the home secretary is due to unveil a series of reforms later this week that are aimed at increasing safety for children online.
These are believed to include a voluntary code of good conduct for websites.
Home secretary Jacqui Smith has unveiled new plans to protect children from sex offenders on the internet.
Issuing new guidance for web users, Smith said social networking sites would be given the details of registered child sex offenders.
Websites such as Facebook and MySpace would be able to block offenders, who would face a prison term of up to five years if they failed to give police their email address.
The social networking guidance also provides advice for parents and businesses in how to protect children from online predators.
It recommended that other service providers, such as the Child Exploitation Online Protection Agency and the NSPCC, carry advice to allow users to report abuse.
It also called for industry to do more to report suspicious behaviour to the police and said that it should be made more difficult for users over the age of 18 to search for underage users.
Smith also launched a kitemark setting minimum standards for filtering software for home computers.
I want to see every child living their lives free from fear, whether they are meeting friends in a youth club or in a chat room, she said: We are working together with police, industry and charities to create a hostile environment for
sex offenders on the internet and are determined to make it as hard for predators to strike online, as in the real world.
Social network sites risk infantilising the mid-21st century mind, leaving it characterised by short attention spans, sensationalism, inability to empathise and a shaky sense of identity, according to a leading neuroscientist.
The startling warning from Lady Greenfield, professor of synaptic pharmacology at Lincoln college, Oxford, and director of the Royal Institution, has led members of the government to admit their work on internet regulation has not extended to
broader issues, such as the psychological impact on children.
She told the House of Lords that children's experiences on social networking sites are devoid of cohesive narrative and long-term significance. As a consequence, the mid-21st century mind might almost be infantilised, characterised by short
attention spans, sensationalism, inability to empathise and a shaky sense of identity.
Arguing that social network sites are putting attention span in jeopardy, she said: If the young brain is exposed from the outset to a world of fast action and reaction, of instant new screen images flashing up with the press of a key, such
rapid interchange might accustom the brain to operate over such timescales. Perhaps when in the real world such responses are not immediately forthcoming, we will see such behaviours and call them attention-deficit disorder.
"It might be helpful to investigate whether the near total submersion of our culture in screen technologies over the last decade might in some way be linked to the threefold increase over this period in prescriptions for methylphenidate, the
drug prescribed for attention-deficit hyperactivity disorder.
She also warned against "a much more marked preference for the here-and-now, where the immediacy of an experience trumps any regard for the consequences. After all, whenever you play a computer game, you can always just play it again;
everything you do is reversible. The emphasis is on the thrill of the moment, the buzz of rescuing the princess in the game. No care is given for the princess herself, for the content or for any long-term significance, because there is none. This
type of activity, a disregard for consequence, can be compared with the thrill of compulsive gambling or compulsive eating.
Greenfield also warned there was a risk of loss of empathy as children read novels less. She said she found it strange we are enthusiastically embracing the possible erosion of our identity through social networking sites, since those that
use such sites can lose a sense of where they themselves finish and the outside world begins.
The solutions, however, lay less in regulation as in education, culture and society.
The Child Exploitation and Online Protection Centre (CEOP) called on the social networking website Facebook to feature its alert button following the conviction of Peter Chapman for the murder of Ashleigh Hall. Chapman posed as a teenager on
Facebook in order to 'groom' Ashleigh, 17, before raping and murdering her.
Jim Gamble, the chief executive of CEOP, said 267 reports of suspicious activity on Facebook had been received in 2009 but users had been unable to log their concerns directly with his agency. Facebook itself had brought only a handful of cases
to the attention of the unit, which investigates online paedophile activity.
Facebook indicated that it would resist the demand to put the CEOP alert button on its site because it believed its own reporting system was adequate. Sources said that Ashleigh Hall had also made contact with her murderer via MSN chat sites,
which do carry the CEOP button, but she did not use it to alert the authorities.
A spokesman for Facebook said: The safety of Facebook users is our top priority. We have reporting buttons on every page of our site and continue to invest heavily in creating the most robust reporting system to support our 400 million users.
Facebook users will be able to report suspicious online behaviour and access internet safety advice with the launch of a new application. Users of the social networking site will be able to access an advice centre from their homepage, where there
will be a dedicated facility for reporting inappropriate sexual behaviour.
The facility is the result of a initiative between Facebook and the Child Exploitation and Online Protection Centre and users will be able to add the ClickCEOP service as an application to find information about online safety.
An advert for ClickCEOP will appear on the homepage of every user aged between 13 and 18.