Liberal Democrats have rejected a plan for internet providers to block online pornography unless web users "opt in".
The policy was defeated at the party conference in Glasgow after some members called it "illiberal" and suggested the controls would not work.
Lib Dem peer Floella Benjamin said the filters would protect children.
But members voted to return the plan to policy makers for redrafting. It must pass a future vote to be included in the 2015 election manifesto.
The vote leaves the Lib Dems at odds with the Conservatives, who want UK internet service providers (ISPs) to impose "default" filters to block pornography.
This would mean filters would be switched on for new internet customers unless they chose not to have them.
Existing customers would be contacted by ISPs and asked if they wanted filters switched on.
Before the vote Baroness Benjamin, a former children's television presenter, said: "This motion is about protecting children from online pornography and inappropriate material - it's not about censorship or stopping adults from accessing legal material.
"Arguments about opt in, censorship or freedom of expression are simply not applicable here.
"This pandemic crosses a sacred line - although the internet is a wonderful resource, it also has a dark side."
But members overwhelmingly chose to send the policy back to the party's Federal Policy Committee.
Plans for automatic filters to block legal pornography websites are distinct from government efforts to tackle illegal material such as images of child abuse.