UK telcos are continuing to work towards flicking the switch on network-level filters that will allow subscribers to block "harmful" content by the end of this year.

That's despite the fact that the Liberal Democrat Party - which is the junior member of the Coalition government - has overwhelmingly opposed the parental controls that are set to be applied by BT, Virgin Media and BSkyB.

Over the past few months, MPs have repeatedly sought political currency from the online pornography debate, while the country's three biggest ISPs have quietly been developing DNS lookup technology with yet-to-be-named third parties.

Since the start of the year, telcos - keen to swerve regulation - have slowly come out in favour of network level filters to help customers block the material they want to censor in their homes.

Controversy has stalked the content-blockers because the ISPs are expected to gently encourage their subscribers to opt in to filtering. Sky told The Register in May this year that it would pre-tick the box when informing customers that they can prevent, for example, access to websites they might deem inappropriate for their kids to view.

Late on Sunday, Lib Dem activists rejected the filters as "illiberal". The vote, which took place at its annual conference in Glasgow, sets the Nick Clegg-led party apart from the Tories.

Conservative Prime Minister David Cameron has shifted his position on censoring the web a number of times over the course of the last few years.

But as his party edges ever closer to the General Election in 2015, Cameron appears to have spotted an opportunity to appeal to Middle England by throwing his support behind network-level filtering that compels a household's broadband bill-payer to make a declaration about whether or not they want to view porn online.

All the while, BT, Sky and Virgin Media have been preparing filters for their services in a move to prevent regulatory intervention.

TalkTalk, of course, debuted its Homesafe system in 2011. That system, provided by Huawei, works by harvesting every URL visited by every TalkTalk customer. It then follows them to each web page and scans for threats, creating a master blacklist and a whitelist of dangerous and safe URLs.

The country's three other big telcos are yet to reveal details about the DNS lookup tech they will employ on their systems.

The Lib Dems and Tories may be in disagreement, but telcos, El Reg understands, are broadly satisfied to be offering filtering to their customers.

The Internet Service Providers' Association (ISPA) secretary general, Nicholas Lansman, said:

A number of ISPs are moving to a system where customers will be presented with an unavoidable choice over what kind of content types they would or wouldn’t like to see filtered. The decision to turn on filters is then put into the hands of parents and carers who know best what is appropriate for their children. We agree with some of the sentiments yesterday that pointed out that filtering is not a silver bullet and is often imperfect and should not replace parental mediation.

If Cameron gets his way, the filters will be subject to regulatory oversight from Ofcom to monitor their implementation and workability. The PM has also called on smaller telcos to use similar systems.

It's quite possible, following yesterday's Lib Dem activists' vote, that some of Cameron's more stringent plans around filtering could yet be torpedoed.

But - regardless of what politicians are saying - network-level content filters are coming. ®