Stung by criticism that ISPs have been blocking legitimate websites as part of 'Cameron's pornwall', a working group is drawing up a whitelist of exceptions for use by the industry, it has emerged.

According to the BBC, a working group under the auspices of the Government-backed UK Council for Child Internet Safety (UKCCIS) has been creating and testing a whitelist of sites with the aim of eventually sharing it with participating ISPs.

Group chair David Miles said that he believed that the number of wrongly-filtered websites – for example sites dealing with sex education - had so far been “low”

Nevertheless, "if you are a charity and you deal with teenagers in distress that 1 or 10 matters to you," he was quoted as saying.

"What we are seeing in the UK is quite unusual, said Miles, contrasting the introduction of ISP controls to those implemented by mobile operators years ago.

“At the ISP level, on public Wi-Wi and via mobile operators, the UK will be subject to a substantial amount of network-level filtering all of a sudden. That new network-level filtering could increase the level of over-blocking.”

The working group would also look at establishing a complaints procedure for websites that believed they had been incorrectly filtered.  In future, Miles suggested that it might be also possible for sites to automatically flag their own content to filtering systems.

Some critics will welcome the scheme, but deeper reservations remain. Some might agree that hardcore porn and violence should be open to filtering but what are the limits and definitions? Libertarians see the whole system as a way of imposing a top-down system of censorship that uses moral pressure to get subscribers to accept controls.

A few months into the roll out of filtering by some large ISP, problems have certainly emerged; the TorrentFreak news site being one of a number of reported victims of the false positive problem in early January.

Meanwhile it’s not clear that the initiative will even meet its stated objective or blocking inappropriate websites with anonymous proxies being one possible workaround for determined web users. Even whitelisting has elicited scepticism.

“Whilst protecting children from the darker recesses of the internet by forcing ISPs to block sites might make great headlines for the Government, the [whitelisting] initiative will fail,” commented Andrew Goode of brand protection firm, Project Sunblock, referring specifically to sites hawking pirated material.

“Unfortunately for the Government, using whitelists is never going to work as the ability for sites to be mirrored is just too easy for those people who are committed to making illegal and inappropriate content available online. For example, there are over 160 proxies from which you can access Pirate Bay, and new proxies are being set up all the time to circumnavigate exactly this initiative and stay one step ahead,” he said.

He believed a better approach was to block the ad systems that supported them. Without a broader approach, ISPs would be left “chasing shadows.”