But it was not until we went to live in Hong Kong that my view of the world, and the place that race occupies within it, was to be utterly transformed. Rather than seeing race through the prism of my own society, I learned to see it globally. When we left these shores, it felt as if we were moving closer to my wife's world: this was east Asia and she was Malaysian. And she, unlike me, had the benefit of speaking Cantonese. So my expectation was that she would feel more comfortable in this environment than I would. I was wrong. As a white, I found myself treated with respect and deference; my wife, notwithstanding her knowledge of the language and her intimacy with Chinese culture, was the object of an in-your-face racism.

In our 14 months in Hong Kong, I learned some brutal lessons about racism. First, it is not the preserve of whites. Every race displays racial prejudice, is capable of racism, carries assumptions about its own virtue and superiority. Each racism, furthermore, is subtly different, reflecting the specificity of its own culture and history.

Second, there is a global racial hierarchy that helps to shape the power and the prejudices of each race. At the top of this hierarchy are whites. The reasons are deep-rooted and profound. White societies have been the global top dogs for half a millennium, ever since Chinese civilisation went into decline. With global hegemony, first with Europe and then the US, whites have long commanded respect, as well as arousing fear and resentment, among other races. Being white confers a privilege, a special kind of deference, throughout the world, be it Kingston, Hong Kong, Delhi, Lagos - or even, despite the way it is portrayed in Britain, Harare. Whites are the only race that never suffers any kind of systemic racism anywhere in the world. And the impact of white racism has been far more profound and baneful than any other: it remains the only racism with global reach.

Being top of the pile means that whites are peculiarly and uniquely insensitive to race and racism, and the power relations this involves. We are invariably the beneficiaries, never the victims. Even when well-meaning, we remain strangely ignorant. The clout enjoyed by whites does not reside simply in an abstraction - western societies - but in the skin of each and every one of us. Whether we like it or not, in every corner of the planet we enjoy an extraordinary personal power bestowed by our colour. It is something we are largely oblivious of, and consequently take for granted, irrespective of whether we are liberal or reactionary, backpackers, tourists or expatriate businessmen.

The existence of a de facto global racial hierarchy helps to shape the nature of racial prejudice exhibited by other races. Whites are universally respected, even when that respect is combined with strong resentment. A race generally defers to those above it in the hierarchy and is contemptuous of those below it. The Chinese - like the Japanese - widely consider themselves to be number two in the pecking order and look down upon all other races as inferior. Their respect for whites is also grudging - many Chinese believe that western hegemony is, in effect, held on no more than prolonged leasehold. Those below the Chinese and the Japanese in the hierarchy are invariably people of colour (both Chinese and Japanese often like to see themselves as white, or nearly white). At the bottom of the pile, virtually everywhere it would seem, are those of African descent, the only exception in certain cases being the indigenous peoples.

This highlights the centrality of colour to the global hierarchy. Other factors serve to define and reinforce a race's position in the hierarchy - levels of development, civilisational values, history, religion, physical characteristics and dress - but the most insistent and widespread is colour. The reason is that colour is instantly recognisable, it defines difference at the glance of an eye. It also happens to have another effect. It makes the global hierarchy seem like the natural order of things: you are born with your colour, it is something nobody can do anything about, it is neither cultural nor social but physical in origin. In the era of globalisation, with mass migration and globalised cultural industries, colour has become the universal calling card of difference. In interwar Europe, the dominant forms of racism were anti-semitism and racialised nationalisms, today it is colour: at a football match, it is blacks not Jews that get jeered, even in eastern Europe.

Liberals like to think that racism is a product of ignorance, of a lack of contact, and that as human mobility increases, so racism will decline. This might be described as the Benetton view of the world. And it does contain a modicum of truth. Intermixing can foster greater understanding, but not necessarily, as Burnley, Sri Lanka and Israel, in their very different ways, all testify.

Hong Kong, compared with China, is an open society, and has long been so, yet it has had little or no effect in mollifying Chinese prejudice towards people of darker skin. It is not that racism is immovable and intractable, but that its roots are deep, its prejudices as old as humanity itself. The origins of Chinese racism lie in the Middle Kingdom: the belief that the Chinese are superior to other races - with the exception of whites - is centuries, if not thousands of years, old. The disparaging attitude among American whites towards blacks has its roots in slavery. Wishing it wasn't true, denying it is true, will never change the reality. We can only understand - and tackle racism - if we are honest about it. And when it comes to race - more than any other issue - honesty is in desperately short supply.

Race remains the great taboo. Take the case of Hong Kong. A conspiracy of silence surrounded race. As the British departed in 1997, amid much self-congratulation, they breathed not a word about racism. Yet the latter was integral to colonial rule, its leitmotif: colonialism, after all, is institutionalised racism at its crudest and most base. The majority of Chinese, the object of it, meanwhile, harboured an equally racist mentality towards people of darker skin. Masters of their own home, they too are in denial of their own racism. But that, in varying degrees, is true of racism not only in Hong Kong but in every country in the world. You may remember that, after the riots in Burnley in the summer of 2001, Tony Blair declared that they were not a true reflection of the state of race relations in Britain: of course, they were, even if the picture is less discouraging in other aspects.

Racism everywhere remains largely invisible and hugely under-estimated, the issue that barely speaks its name. How can the Economist produce a 15,000-word survey on migration, as it did last year, and hardly mention the word racism? Why does virtually no one talk about the racism suffered by the Williams sisters on the tennis circuit even though the evidence is legion? Why are the deeply racist western attitudes towards Arabs barely mentioned in the context of the occupation of Iraq, carefully hidden behind talk of religion and civilisational values?

The dominant race in a society, whether white or otherwise, rarely admits to its own racism. Denial is near universal. The reasons are manifold. It has a huge vested interest in its own privilege. It will often be oblivious to its own prejudices. It will regard its racist attitudes as nothing more than common sense, having the force and justification of nature. Only when challenged by those on the receiving end is racism outed, and attitudes begin to change. The reason why British society is less nakedly racist than it used to be is that whites have been forced by people of colour to question age-old racist assumptions. Nations are never honest about themselves: they are all in varying degrees of denial.

This is clearly fundamental to understanding the way in which racism is underplayed as a national and global issue. But there is another reason, which is a specifically white problem. Because whites remain the overwhelmingly dominant global race, perched in splendid isolation on top of the pile even though they only represent 17% of the world's population, they are overwhelmingly responsible for setting the global agenda, for determining what is discussed and what is not. And the fact that whites have no experience of racism, except as perpetrators, means that racism is constantly underplayed by western institutions - by governments, by the media, by corporations. Moreover, because whites have reigned globally supreme for half a millennium, they, more than any other race, have left their mark on the rest of humanity: they have a vested interest in denying the extent and baneful effects of racism.

It was only two years ago, you may remember, that the first-ever United Nations conference on racism was held - against the fierce resistance of the US (and that in the Clinton era). Nothing more eloquently testifies to the unwillingness of western governments to engage in a global dialogue about the problem of racism.

If racism is now more widely recognised than it used to be, the situation is likely to be transformed over the next few decades. As migration increases, as the regime of denial is challenged, as subordinate races find the will and confidence to challenge the dominant race, as understanding of racism develops, as we become more aware of other racisms like that of the Han Chinese, then the global prominence of racism is surely set to increase dramatically.

It is rare to hear a political leader speaking the discourse of colour. Robert Mugabe is one, but he is tainted and discredited. The Malaysian prime minister, Mahathir Mohamed, is articulate on the subject of white privilege and the global hierarchy. The most striking example by a huge margin, though, is Nelson Mandela. When it comes to colour, his sacrifice is beyond compare and his authority unimpeachable. And his message is always universal - not confined to the interests of one race. It is he who has suggested that western support for Israel has something to do with race. It is he who has hinted that it is no accident that the authority of the UN is under threat at a time when its secretary general is black. And yet his voice is almost alone in a world where race oozes from every pore of humanity. In a world where racism is becoming increasingly important, we will need more such leaders. And invariably they will be people of colour: on this subject whites lack moral authority. I could only understand the racism suffered by my wife through her words and experience. I never felt it myself. The difference is utterly fundamental.

· Martin Jacques is a visiting fellow at the London School of Economics. The death of his wife, Harinder Veriah, in 2000 in a Hong Kong hospital triggered an outcry which culminated in this summer's announcement by the Hong Kong government that it would introduce anti-racist legislation for the first time

martinjacques1@aol.com