UK parents are the strictest in Europe when it come to their children's Internet use, with more than half installing filtering software.
But even for the children protected, over 20 per cent of harmful content will make it through, according to two new reports released by European Commissioners.
The authors of the first report, Benchmarking of parental control tools for the online protection of children, tested 31 sets of tools for PCs, games consoles and mobile phones, designed to monitor usage as well as blocking pornography and other harmful content.
The report (available as a 6.3MB PDF) covers both standalone products and the parental controls built into games consoles and computer operating systems.
Porn was blocked more effectively than any other form of harmful content, but other online threats, such as racist or violent content and material encouraging drug use or self-harm, managed to slip through - particularly if they appeared in languages other than English.
Instant messaging was another area in which children were left at risk. While the majority (61 per cent) of tools tested could be used to block MSN, fewer than half (46 per cent) extended that control to Skype. Only four products tested enabled parents to filter instant messaging contacts.
Most tools proved similarly ineffective at safeguarding children using social networking sites such as Facebook, Bebo and Twitter.
Of the PC-based filtering tools, Vise scored highest, with 3.5 out of a possible 4. Second was CyberSieve with 3.4 - while, perhaps surprisingly, Windows' built-in parental controls came in third with 3.2.
The report's authors noted that parental controls for smartphones and games consoles - including the Wii and PS3, which allow web browsing - are less effective. While setting up parental controls on these devices was said to be easier, it was a "challenge" to persuade parents that it was required.
The EU Kids Online survey, also published today, shows that UK parents are the strictest in Europe when it comes to controlling their children’s Internet use, with 54 per cent using parental control software. Across the EU, roughly a quarter of parents (28 per cent) block or filter websites – in states such as Romania, the figure is as low as nine per cent.
In addition to using parental controls, 70 per cent of parents said that they talked to their children about what they do on the Internet, with 58 per cent claiming they remained nearby. More than half (52 per cent) said they talked about things that might bother their child.