A major study of the web-blocking tools used by mobile operators has revealed that the filters are erroneously censoring scores of legitimate websites, and run with little transparency.
The criticism comes from the Open Rights Group, which has been studying which sites mobile users have had problems accessing.
The results point to a systematic “over-blocking” of websites [PDF], including political commentaries, personal blogs and even residents groups' websites.
The ORG established a mobile blocking website to enable users to submit reports of blocks they considered inappropriate.
Mobile operators routinely use web filtering technology to restrict access to websites which may contain adult material. Between 1 January and 31 March, users reported blocks on sites as varied as Tor Project, La Quadrature du Net and eHow.
"This report shows how child protection filters can actually affect many more users than intended and block many more sites than they should,” said Peter Bradwell of the ORG.
“These blunt blocks effectively add up to a system of censorship across UK networks.”
Bradwell argued that mobile operators should use an opt-in system, where users could choose to have filters switched on or off, rather than ineffectual web-blocking tools.
He also criticised the lack of transparency with which the web filters operate, making it hard for users or website owners to take action in the event that sites had been wrongly blocked.
The study comes amid fears that the government will introduce web-filtering regulations for UK internet service providers (ISPs).
Some MPs have called for ISPs to operate a porn opt-in policy, which would mean customers would have web filters routinely applied to their broadband connections.
Vodafone, O2 and Everything Everywhere were approached for comment on the ORG report but had not responded at the time of publication.
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