A U.K. government-led push to force ISP-level Internet filtering of pornography and obscenity has turned to strong-arm tactics.

Angry at demands to use misleading language with customers and commit to using untested "browser intercept" filtering (as well as give money to MP Claire Perry's undefined parental "awareness campaign"), an ISP industry member has just provided BBC News with a copy of the letter all four U.K. ISPs received this morning.

The letter begins by telling ISPs they are to commit to complying with the government's demands in time for David Cameron to announce the ISP changes by "midday Friday."

Instead of telling customers they have and can use 'active choice' in filtering, the government has told ISPs to say that filtering is "default on" — the very policy change the government has been trying to force on its ISPs and customers for years, but has failed, as it is widely seen as default censorship.

UK ISPs are angry and have fired back, telling BBC News that the letter's demands are "staggering — asking us to market active choice as default-on is both misleading and potentially harmful."

The letter comes from the U.K. Department of Education, but it outlines specific demands from Downing Street, expressly for David Cameron to announce.

Read the letter in its entirety in BBC's Leaked letter shows ISPs and government at war. It begins,

Dear All, I am emailing to ask for some specific action which the prime minister plans to announce shortly. This follows a meeting yesterday at No 10 yesterday to discuss a range of child internet safety issues including parental controls and filters. The prime minister would like to make some further specific requests of industry and his office have asked us to ask you when you could deliver the following actions.

The first demand is for all ISPs to implement Talk Talk's untested "browser intercept" to force existing customers into choosing parental controls:

The prime minister wants to announce that by the end of the year, every household with a broadband internet connection will have had to make a decision to "opt-out" of installing filters. Will the other three ISPs consider making a commitment to adopting this approach — even before it has been trialled?

The letter asks all the ISPs to give MP Claire Perry's parental "awareness campaign money — even though the campaign has not been outlined and the focus has not been specified:

The prime minister would like to be able to announce a collective financial commitment from industry to fund this campaign. I know that it will be challenging for you to commit to an unknown campaign but please can you indicate what sum you will pledge to this work that the PM can announce.

Perry has been trying to force ISP-level Internet filtering across the U.K. since 2010.

Finally, the letter tells ISPs to change the language used to explain parental filters to customers - specifically that ISPs are to use the language "default on" even though the letter states that ISPs do not need to make any actual "default on" technical implementation to Internet filters.

This is why BBCs source is saying the government is asking ISPs to mislead customers - no doubt so Cameron and Perry can merely say that they have implemented the default filters they have failed year after year at obtaining.

Without changing what you will be offering (ie active-choice +), the prime minister would like to be able to refer to your solutions [as] "default-on" as people will have to make a choice not to have the filters (by unticking the box). (...) Would you be able to commit to including "default-on" or similar language both in the set-up screen and public messaging?

The letter's demands are on a tight timeline, putting U.K. ISPs under pressure — a strong-arm tactic.

BBC News said that today the ISPs will meet with MP Claire Perry to give their official response to this letter.

Perry jumped the gun last month when she told news outlets that parental filters for pornographic content would be coming as a default setting for all homes in the U.K. by the end of 2013.

Apparently she didn't ask any of the ISPs how they felt about the idea.

On Friday June 14, Perry had prematurely announced that ISPs would begin default filtering and requiring customers to opt-out — and she got a rude awakening when, on the following Monday, U.K. ISPs countered Perry's Friday statements to press that ISPs in the U.K. would be filtering adult content by default in 2014.

Unfortunately for Perry, saying something is true doesn't magically make it so.

The U.K.'s Internet Service Providers trade association went on record saying they remain opposed to default filtering and would do no such thing.

Citing technical realities — read: limitations of filters — and stressing responsible parenting above potential 'over-blocking' which would result in censorship, Nicholas Lansman, secretary general of trade association ISPA, which represents the UK's net suppliers, reminded the world that filtering tools are already supplied with service.

Lansman supported the ISP's stance, saying, "We remain opposed to default filtering, as it is only one part of the solution, and can be circumvented and lead to over- or under-blocking."

As in the United States, pornography is legal in the U.K.

Image via Wikicommons/robertsharp.