Update 2: And Here's the Open Rights Group's petition.
Update: Here's another, broader petition that hits on issues the other one misses
Here's a Change.org petition to UK Prime Minister David Cameron, calling on him to withdraw his plan to censor the Internet in the UK, blocking huge numbers of legal sites from "forums" to "circumvention tools" to "alcohol information" and (legal) pornography. Cameron wants ISPs to default to sending all their users' network activity to unaccountable, offshore companies like Huawei, who will unaccountably determine which requests will be fulfilled and which will be blocked. If subscribers want to turn this off, they'll have to tell their ISPs that they want "pornography" and possibly have to provide proof of age -- such as going in person to a sales office to allow their passports to be insecurely copied and filed by retail staff.
The government is currently trying to push a bill forcing ISPs to provide opt-out pornography filtering, however this is an issue that fails to address any real problems.
Bad parenting is the real problem, and bad parents will simply allow the filter to be enabled and believe it protects their children, even though the filters are easily (even trivially) circumvented. Parents need to supervise and educate their children about internet use, not rely on filters of dubious effectiveness.
It also sets a poor precedent that objectionable content can be blocked at the ISP level in the name of protecting children, who are in fact being harmed more by poor parenting. Aside from content of a clearly illegal nature the government should not be forcing the presence of filters at all, but instead pushing to improve the involvement of parents in a child's life, and to promote education over flimsy, disruptive, and money-wasting "solutions".
(Image: Youth worker Kokou Djagadou listens to David Cameron at the London Summit on Family Planning, a Creative Commons Attribution Share-Alike (2.0) image from dfid's photostream)