Yesterday David Cameron called for renewed consultation on default blocking of internet porn.

Yesterday Cameron's party had its ass kicked in local elections. Could these facts by chance be related? If I were his PR, I'd dump the caring-about-families angle and arrange for Dave to be photographed with a lovely basket of kittens.

It's not that I'm against regulation of internet porn. I'm just wearied by "talks about talks" on this issue. In October 2011, Cameron's claim that he had secured agreement from Britain's major internet service providers (ISPs) to install automatic porn filters was immediately disavowed by the industry. Since then, debate has rumbled on the ethics and efficacy of "opt-in" systems, whereby internet users must actively request that porn sites are enabled on their broadband service.

In fairness, the issue is complicated. No one is cheered by last month's report from the parliamentary inquiry which found that 80 per cent of 16-year-olds regularly access pornography, much less that a third of 10-year-olds have seen sexually explicit material online. No one can, I think, seriously argue that free and unregulated access to sites devoted to sexual hurt and humiliation (which, not to be squeamish, account for the bulk of contemporary porn) will not affect the outlook and expectations of a generation of girls and boys. However, the arguments against automatic network level filtering are loud, many and various.

There's the civil rights lobby that fears censorship, any censorship, as a matter of principle. Personally, I'm not persuaded that restricting access to sites such as gangbangwhore.com will necessarily spell the end of democracy (the "Do you want us all to end up like China?" argument). It seems to me that we have effectively managed protection of minors in other media – 9pm watershed, over-18 film certificates, adult-rated video games – without surrendering too much in the way of personal freedoms and it cannot, surely, be beyond the vast collective brain of Silicon Valley to come up with something similar for online material. And if we cannot, in the interests of free expression, legislate against pornography per se, can we not apply some other legislation that will, at least, put a crimp in the frankly abusive end of the business? "Incitement to violence" does not, to me, seem too strong a description of hardcore "adult entertainment" currently on offer.

I concede that, as ISPs have vigorously argued, no internet filter will be 100 per cent fail-safe. The fact that children are more computer savvy than their parents is a real consideration and it only takes someone clever in the playground to find the "way in'" to restricted sites. But since when was child protection an "all or nothing" issue? Should we ban traffic lights just because some motorists ignore them? If even a fraction of the porn currently streaming into children's bedrooms is blocked, that is arguably a start worth making.

The real sticking point in Cameron's new inquiry (as I suspect it was in the last) is likely to be the argument that restricting online access, by whatever means, is "bad for business". ISP business is worth £3bn a year and pornography accounts for a whacking 30 per cent of web traffic. The streaming of video footage is particularly lucrative and visitors to porn sites tend to linger awhile. There is, therefore, powerful financial incentive to keep ministers rubbing their chins over porn-blocking measures as long as possible . It has already been intimated by Whitehall that while efforts to thrash out a solution that suits ISPs and consumers will be redoubled in the new inquiry, the chin-rubbing is not expected to lead to a Green Paper soon.

Which leaves us with our old friend "parental responsibility". The rider to each of the above arguments against government legislation is that parents must take responsibility for what their children see in their own homes. Indeed, we are piously reminded that the danger of an unavoidably imperfect porn filtering system is that parents will be lulled into a false sense of security and drop all efforts at vigilance.

Parents, I think, are not so stupid. But the real problem in this is that some parents are more responsible than others. Which is why the "opt-out" system currently preferred by ministers, whereby consumers must choose to block access to porn sites, is not good enough.

If blanket legislation is too problematic for a government wedded to the market economy, then parents must flex their economic muscle. There is currently only one ISP offering network level "porn protection" to all customers (and not just at point of purchase) and it is an intensely competitive market. It is, I would suggest, time to put the frighteners on ISPs by demanding effective protection, not just for own "responsibly parented" children, but for all children. It takes five minutes to write a letter to a CEO (it takes considerably longer, in my experience, to figure out "parental controls"), and if consumer pressure doesn't work, then we need to think about withdrawing our custom. Inconvenient, I grant you, but as I say, it's a cut-throat market and I don't think it would take the industry long to scent a selling point.

Select committees inquire, ministers discuss, but in the current impasse over porn-blocking I suspect that only money talks. We – the consumer – are "the money". And it's time to shout the whole house down.