The government has put forward proposals to block access to web sites that promote extremist material on public networks such as those in schools and libraries as part of efforts to combat terrorism.
The proposals are outlined in the Prevent report, an update to the government's existing anti-terrorism strategy, which argues that blocking certain web sites is key to halting the spread of extremist propaganda.
"Internet filtering across the public estate is essential. We want to ensure that users in schools, libraries, colleges and Immigration Removal Centres are unable to access unlawful material," the report said.
"We want to explore the potential for violent and unlawful URL lists to be voluntarily incorporated into independent national blocking lists, including the list operated by the Internet Watch Foundation [IWF]."
The IWF is currently limited to preventing images of child sexual abuse being hosted anywhere in the world, and criminally obscene adult content and non-photographic child sexual abuse images from being hosted in the UK.
A spokesperson for the IWF explained that it is not straightforward to assume that the organisation could start monitoring other forms of internet sites.
"Any change in our remit would be a matter for discussion for our funders and our board," the spokesperson said.
Home secretary Theresa May said in the House of Commons on Tuesday that the government will make greater use of social media sites to combat the rise of extremist propaganda, and will work more closely with the international community.
"We will also work to tackle the particular challenge of radicalisation on the internet, and to make better use ourselves of social media and other modern communications technologies," she added.
"Many internet providers are based [in the US] rather than here, and are therefore outside UK jurisdiction. We are doing more to talk to the US, and indeed to those companies directly, about their responsibilities."
However, Jim Killock, executive director of the Open Rights Group, argued that the proposals to block sites in libraries are "a step too far", and that doing so in educational institutions could actually make them more appealing.
"Libraries are a resource for sharing knowledge and study, no matter who you are. Adults must be assumed to be responsible and capable of making their own judgements," he said.
"Young adults, too, should be treated with respect. The government should consider whether banning such web sites in schools would actually give these sites a credence and cachet they do not deserve."
Blocking web sites remains a controversial topic. Ofcom is currently investigating whether web-blocking provisions in the Digital Economy Act will work in practice.
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