If there is one thing about the "big society" upon which all commentators agree, it is that the idea of getting local volunteers to step in to run public services is a joke. We may see brief, isolated instances of community litter-picking teams or volunteer librarians, but the vision of an unpaid army taking over the delivery of great swaths of local public services is a fantasy for the foreseeable future. Those with the time and skills do not have the inclination and vice versa. This has led many to conclude that the very idea of the big society is a national joke. Just about the only person not laughing is David Cameron, but I suspect he knows something most people don't.

The media's obsession with volunteering has obscured the bigger picture. If we look at what the prime minister is actually saying and doing, volunteering isn't especially important to the big society. Of course Cameron approves of it, everyone does, but none of the hundreds of millions being used to float the big society is ringfenced to encourage volunteering. Instead anything up to £300m has been made available to a social investment bank to provide capital funding (at market interest rates) to "social ventures"; while £100m goes to a "transition fund" that will assist those charities losing existing contracts with local authorities.

The real voluntary sector has little to do with this. Directors of smaller voluntary organisations and charities live in terror of debt and are often constitutionally barred from taking it on. Only organisations expecting very high turnovers will find this useful. Cameron has not raised an army of volunteers. He has launched an armada of service provision companies.

Volunteering was only the third prong to the big society mentioned by Cameron in his Observer article. The first two were "devolving power to the lowest level so neighbourhoods take control of their destiny" and "opening up our public services, putting trust in professionals and power in the hands of the people they serve."

What does this mean? These sentences have attracted little attention, but combine them with the bank and the transition fund, and the true purpose of the big society becomes clear. Neighbourhoods now have the choice to pay to have their own park cleaned, their own library or leisure centre staffed, even their own streets patrolled by private security guards. They also have the choice as to who should be providing these services once state or local authority provision has all but gone.

We have been heading in this direction since 1997. New Labour started the big society, with the myriad experiments in neighbourhood management, micro-councils and community organisation. Any community can now petition to establish a town, village or parish council with tax-raising powers, and over 200 have done so already. The same powers were extended to London residents in 2008. Any neighbourhood that wants to – and can afford to – can now arrange many of their own additional public services.

If taken to their logical conclusion, these policies mean that affluent neighbourhoods can have all the amenities they want, the best living environment, the best services, without having to share their council tax payments with the poorer people down the road. Less fortunate areas will fester for lack of cash. Then, when they do, this can be portrayed as their own choice and their own failure. "So you couldn't pay for it?" the voices will say: "Then why didn't you just volunteer like we suggested?"

There are many on the neoliberal right who will welcome this. Some believe all this is for the good of the country and see it as a fairer system than a redistributive social democratic welfare state. I profoundly disagree, but I am happy to have the debate. In fact, I'd like to have this debate as quickly and as loudly as possible. We are marching towards a society of unprecedented division, inequality and social injustice, with postcode lotteries of double rollover dimensions – and nobody thought to ask us.

I'm a supporter of localism in many respects. I have been personally and professionally involved in community organisation and neighbourhood management schemes, and I've seen more benefits than drawbacks. However, we need to decide where to draw the line. I'd argue that such initiatives provide distinct opportunities for communities to rise above the bare minimum of civic involvement, allowing neighbourhoods to forge their own identities and address their own unique local needs. I do not believe such schemes should replace the provision of universal public services – precisely the situation we are sleepwalking towards.

In the chaos of economic crisis and coalition politics, we seem to have forgotten that Cameron was once considered a shrewd political operator with a sharp grasp of marketing. One day we may realise that his greatest trick was convincing the world that the big society was one big joke.

• This article was amended on 21 February 2011. It originally stated that the National Lottery paid for the transition fund for charities. Funding actually comes from central government. In addition, it stated that communities could "vote by referendum" to establish a town, village or parish council. In fact, a referendum isn't legally required, although in practice one often takes place. Corrections have now been made to the text