Opinion: the limitless prosperity once promised by urbanisation has failed to materialise, leaving rapidly growing inequality in its wake. It will take more than some clever technology to solve the problems with the world's biggest cities, says Reinier de Graaf.

Urbanisation was supposed to be the world's quick ticket to prosperity. The average urban dweller (on paper) represents five times the economy of the rural dweller. If a rural nation becomes urban in the space of a decade, its economy – at least in theory – doubles every two years. That statistic, however, can hardly conceal the more grim reality. Over the last few decades we have seen that the spectacular growth of cities by no means entails greater and more widely shared prosperity.

What we refer to as "megacities" are mostly cities with the common feature that their development is outpaced by their growth. A lot of these cities exist in a state of almost permanent crisis, where "urbanisation" (literally: the step towards the urbane) has come to signify the exact opposite. In the absence of even the most basic infrastructure and provisions, many of its inhabitants find a decent urban life beyond their reach.

Just as 19th-century England saw the rise of the disenfranchised urban proletariat – so eloquently captured by the term Verelendung – the new urban economy gives rise to another disenfranchised class, this time elevated to a global scale. In this context, the statement that more than half the world's population is now living in cities does not so much signal the ultimate triumph of the urban, but more and more its demasqué.

The megacity is a subject of universal fascination and generally discussed in terms of the opportunities it creates for a mobile, business-oriented group of people, liberated from loyalties to place or nation. With the urban condition about to become universal, we can all become "cosmopolitan".

But it is exactly this false promise that embodies the most venomous aspect of the current celebration of the city. The more the world aspires to a kind of shiny urbane life, the larger the number of people will be for whom this kind of life will prove unattainable.

With the influx of new and ever-poorer inhabitants, cities resort to an ever-more elaborate repertoire of denial in the face of mounting problems. Inhabitants who "overload the system" are increasingly denied access to cities' administrative infrastructures, forcing them into a situation where they officially do not exist.

Rio's favela residents live in a state of exception, denied the civic rights of Rio's "official residents"; Moscow's immigrant workers are not counted as part of Moscow's population; and through the Hukou system in China, being a city dweller is a "birth right" that denies many of China's rural city dwellers the right to live in the city legally.

These communities increasingly constitute a class of their own, with an economy unaccounted for by official statistics and without political clout. And thus, in the wake of a massive influx into cities, we are witnessing the emergence of another kind of "citizen of the world" – those who have drawn the short straw of globalisation and for whom being cosmopolitan simply amounts to being a new "cosmoproletariat".

Yet, if power is ultimately a question of numbers, what will happen when the number of people whose existence is formally denied by the system (yet upon whose compliance the system ultimately depends), reaches a critical mass, large enough to rival those who have denied them access?

What will be the political legacy of those ignored by our collective administrative systems? Can a political force be constructed from people who don't formally exist?

In the 19th century, Friedrich Engel's description of the living conditions of England's working poor ultimately lead to a political theory that would radically alter the geopolitical landscape of the century after. As a consequence, the 20th century became a precarious standoff between competing political ideologies, where the leading economies of the west were systematically challenged by the lure of an alternative ideology in the form of communism seeking – and finding – the support of those left behind: in Korea, Southeast Asia, and later in Latin America and Africa.

The next round of this ideological battle will be fought not over continents, but over cities. The challenge will come from whoever will be able to galvanise the support of all those denied a voice in the urban condition.

Within less than 10 years the world's largest cities will all be located outside the west. Of the 33 megalopolises predicted in 2020, 28 will be located in the world's least-developed countries. The metropolis, once the zenith of western civilisation, is now the property of the "third world".

That can be interpreted as a sign of emancipation, but who actually benefits? Even if the economies of poorer states appear to be closing a gap with richer ones, the inequalities between individuals within states have only grown.

Despite an ever-larger number of theories trying to convince us of the contrary, the world's move towards the urban does not spell a win-win situation. As much as globalisation has exported metropolitan conditions into the third world, it has also imported third-world conditions into the metropolis. In becoming urban we have not overcome the fundamental inequalities of our economic system. All we have done is to give old struggles a new arena.

New coalitions of academia and business have emerged. There is a lot of talk about the "smart city". We can now see the favela residents or Moscow's illegal workers on a computer screen, study their informal patterns and possibly predict when they are about to make trouble. However, in no way does their visibility constitute a step towards any real civic recognition and everything that may come with that.

In fact, it seems the "smart city" mostly blinds us to the possibility of political action. It allows the political sphere to do a Houdini act, where the endless simulation of reality also permits the infinite deferral of political choices.

Cities are the new outer space, no longer our own creation – by us, for us – over which we exercise will, but an extraneous phenomenon that simply happens to us. We no longer intervene in their behaviour. At best we can study them like we study the weather.

The real question is: how much longer we can dodge the question of political responsibility? In merely observing the consequences of our own actions alongside (and on par with) natural disasters, we inevitably set the city on a course to become one.

Reinier de Graaf is a partner in the Office for Metropolitan Architecture (OMA) where he directs the work of AMO, the research and design studio established as a counterpart to OMA's architectural practice.