The Government has said it plans to pass the email addresses of registered sex offenders to social networking sites to make it harder for paedophiles to groom children online.

Launching the The UK Social Networking Guidance today, home secretary Jacqui Smith said if the likes of Bebo, Facebook and Myspace had access to this information it would make it easier for them to stop or monitor offenders using their sites.

However, critics have pointed out that it will be easy for people to set up multiple email addresses in order to bypass these restrictions.

When asked how this problem would be addressed, the Child Exploitation and Online Protection Centre (CEOPS), which will work out how the monitoring will be carried out, admitted it would be a challenge.

"We haven't worked out all the details yet but this gives us another tool to help protect children which is a good thing," a CEOPs representative said.

The Government also wants the sites to display links to organisations such as the NSPCC and the Samaritans, as well as to the police. This would allow users to report suspicious behaviour, abuse or to seek help, it said.

CEOPs will also explore other arrangements in a bid to further monitor sex offenders' online behaviour.

These are likely to include letting internet service providers and law enforcement agencies share reports of potentially illegal activity and suspicious behaviour.

The home secretary said: "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.

"We have some of the strictest controls on sex offenders in the world to protect our children. We are working together with police, industry and char ities 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.

The UK Social Networking Guidance will also give advice to parents and children about how to stay safe online, such as encouraging children not to provide excessive information about themselves.

Earlier this week, a study by Ofcom showed that parents are often woefully ignorant of what their children get up to online.

It found that nearly half of children aged between eight and 17 have a profile on one or more of the popular social networking sites even if they are too young to sign up.

To bypass these restrictions, children are lying about their age and are unconcerned that they make their profiles public, exposing them to predators and bullies.

It is also proposed that the sites make it more difficult for people registered over the age of 18 to search for users under the age of 18.

Annie Mullins, chair of the home secretary's Task Force on Child Protection on the Internet and head of content standards at Vodafone, said: "The protection of young people is a priority for us all and this initiative demonstrates just how effective collaboration between a wide range of organisations including government, the police, non-governmental groups and industry can be.

"Social networking sites are a wonderful way to communicate and it's vital that we work together to help ensure children and young people can use them safely and responsibly."

The home secretary also launched a new Kitemark to set a standard for filtering software for home computers and strengthen protection of children online. This ensures that parents have confidence that the filtering product they use meets an independent standard.

Home Office minister Vernon Coaker said the anti-paedophile measures will be brought in once Parliament has passed legislation allowing ministers to vary the terms of the sex offenders register.

The Criminal Justice and Immigration Bill, currently in the Lords, could be in force by the autumn. It would be applied retrospectively to more than 30,000 sex offenders on the register, according to the Home Office.