Young people are concerned that colleges or potential employers could get the wrong impression if they look them up on social-networking websites.

According to the Information Commissioner's Office (ICO), seven in 10 of the young people it surveyed felt antics and postings on websites such as Facebook and Myspace or views recorded on personal blogs could come back to haunt them in future.

They realise that what currently seems funny to them and their friends may not be to teachers, university admissions and prospective employers. One 14-year-old girl from Scotland told the ICO survey that her initial thought was "who cares" but her subsequent thought was "Oh my God".

Yet despite these fears, six in 10 young people have never considered that what they put online now might be permanent and could be accessed years into the future.

It seems their concerns could be justified as a recent survey conducted by UK recruitment firms Crone Corkill and FSS revealed that 7.5 per cent of employers are using social-networking websites as an informal part of the referencing process; and this number is expected to rise.

A social-networking profile can give a more personal insight into someone's character that cannot be portrayed on a CV.

As well as not thinking about the implications when they post information on the web, the survey of Britons aged 14-21 also revealed that youngsters’ online behaviour is a gift to potential fraudsters.

Two-thirds (eight in 10 girls aged 16-17) accept people they do not know as ‘friends’ on social-networking sites and over half leave parts of their profile public specifically to attract new people. More than seven in 10 are not concerned that their personal profile can be viewed by strangers and seven per cent do not think privacy settings are important and actively want everyone to see their full profile.

As for the data that young people make available, 60 per cent post their date of birth, a quarter post their job title and almost one in 10 give their home address. Couple this basic information with details that might be used to create passwords, e.g. sibling’s name (posted by 23 per cent), pet’s name (posted by a quarter of girls) and even mother’s maiden name (posted by 2 per cent), and fraudsters have the information they need to obtain products and services in a young person’s name or access existing bank or online accounts.

David Smith, deputy commissioner for the ICO, said: “Many young people are posting content online without thinking about the electronic footprint they leave behind.

"The cost to a person’s future can be very high if something undesirable is found by the increasing number of education institutions and employers using the internet as a tool to vet potential students or employees."

The research also found that a third of young people have never read privacy policies on social-networking sites and don’t understand how they can manage their personal information

But when asked how they feel about websites potentially using their details to target advertising at them or to pass on to other websites or brands, a huge 95 per cent are concerned about this, with 54 per cent caring 'a lot’ about how their personal information is used.

A website launched by the ICO which aims to to help young people understand their information rights contains tips and advice on safe social networking.

Mr Smith said: “This shows that when young people are made aware that their details could be being passed between parties – legitimate or unscrupulous – they are worried. We have to help teenagers wise up to every aspect of the in ternet age they’re living in – it may be fun but unfortunately it is not the safe space many think it is.”