Only the desire to recover some imaginary good from the tragedy that was empire can explain the elevation of the neoconservative ideologue Niall Ferguson to chief imperial historian on the BBC and now Channel 4. His aggressive rewriting of history, driven by the messianic fantasies of the American right, is being presented as a new revelation. In fact, Ferguson's "history" is a fairytale for our times which puts the white man and his burden back at the centre of heroic action. Colonialism - a tale of slavery, plunder, war, corruption, land-grabbing, famines, exploitation, indentured labour, impoverishment, massacres, genocide and forced resettlement - is rewritten into a benign developmental mission marred by a few unfortunate accidents and excesses.

Soundbite culture thrives on these simplistic grand narratives. Half-truths and fanciful speculation, shorn of academic protocols such as footnotes, can sound donnishly authoritative. The racism institutionalised by empire also seems to be back in fashion. The book accompanying Ferguson's current Channel 4 series on 20th-century history, The War of the World, tells us that people "seem predisposed" to "trust members of their own race", "those who are drawn to 'the Other' may ... be atypical in their sexual predilections" and that "when a Chinese woman marries a European man, the chances are relatively high ... that only the first child they conceive will be viable." Not far from the pseudo-scientific nonsense that once made it possible to punish interracial relationships.

Behind such talk and the embrace of the broadcasters is the insistence that we are being offered gutsy truths that the "politically correct" establishment would love to suppress. This is the neo-conservative as spunky rebel against liberal tyranny. Yet Ferguson peddles nothing more than the most hackneyed, self-aggrandising myths of empire, canards once championed by old imperialists such as Macaulay and Mill and rehashed now by the Bush administration: western imperialism brings freedom, democracy and prosperity to primitive cultures. The myth decorates US and British foreign policy spin while trendier versions have also emerged in platforms such as the Euston Manifesto. By anointing Ferguson and his fellow imperial apologists such as Andrew Roberts as semi-official historians, the British media are colluding in a dangerous denial of the past and lending support to contemporary US imperial propaganda .

The evidence - researched by scholars such as Amartya Sen, Nicholas Dirks, Mike Davis and Mahmood Mamdani, Caroline Elkins and Walter Rodney - shows that European colonialism brought with it not good governance and freedom, but impoverishment, bloodshed, repression and misery. Joseph Conrad, no radical, described it as "a flabby, pretending, weak-eyed devil of a rapacious and pitiless folly". Good governance? More famines were recorded in the first century of the British Raj than in the previous 2,000 years, including 17-20 million deaths from 1896 to 1900 alone. While a million Indians a year died from avoidable famines, taxation subsidising colonial wars, and relief often deliberately denied as surplus grain was shipped to England.

Tolerance? The British empire reinforced strict ethnic/religious identities and governed through these divisions. As with the partition of India when 10 million were displaced, arbitrarily drawn boundaries between "tribes" in Africa resulted in massive displacement and bloodshed. Freedom and fair play? In Kenya, a handful of white settlers appropriated 12,000 square miles and pushed 1.25 million native Kikuyus to 2,000 restricted square miles. Resistance was brutally crushed through internment in detention camps, torture and massacres. Some 50,000 Kikuyus were massacred and 300,000 interned to put down the Mau Mau rebellion by peasants who wanted to farm their own land. A thousand peaceful protesters were killed in the Amritsar massacre of 1919.

A collective failure of the imagination now makes it difficult for us to think about the globe before European and American domination. Greed and violence are hardly exclusive to one culture. But colonialism destroyed or strangled possibilities and potential for progress, such as Mughal Emperor Akbar's "sul-e-kul" or "universal good" which underpinned his governance. The scale of European imperialism inaugurated a new chapter in the history of greed which still shapes all our lives. Natural resources - cotton, sugar, teak, rubber, minerals - were plundered in gigantic quantities. The Indian textile industry was the most advanced in the world when the British arrived; within half a century it had been destroyed. The enslaved and indentured (at least 20 million Africans and 1.5 million Indians) were shipped across the globe to work on plantations, mines and railroads. The stupendous profits deriving from this enabled today's developed world to prosper.

The point isn't for Europeans to feel guilt, but a serious consideration of historical responsibility isn't the same thing as a blame game. Forgetting history is tempting but undermines a society's capacity for change.

Among the many facile assumptions encouraged by these imperial apologists is that those who criticise colonialism are absolving tyrants and bigots in Asia and Africa from responsibility for their crimes. Of course it is possible and absolutely necessary to condemn both. Indians must acknowledge their culpability for atrocities during the partition, for example. But that in no way exonerates the British Raj from its pivotal role in the tragedy that led to over a million deaths.

A wilful ignorance of other people's cultures and histories encourages the notion that freedom, democracy and tolerance are intrinsically western. As Amartya Sen has argued, the subcontinent has long been home to traditions of free-thinking and debate. Participatory governance was not Britain's gift (recall Gandhi's indigenous village republics), even if parliamentary democracy as an institutional form was adopted in some ex-colonies. Free trade is another mythical western contribution to world history. Amitav Ghosh has reconstructed the forgotten history of a vibrant trade culture between medieval India and Africa. When the Portuguese arrived, they demanded that the Hindu ruler of Calicut expel Muslims, "enemies of the Holy-Faith", from his kingdom. He refused and was subjected to two days of bombardment.

Indeed, one legacy of European colonialism that we all reckon with is the self-fulfilling prophecy of the "clash of civilisations". The claim that east and west are bound to come into conflict is merely an extension of imperial practice which found it useful to seal off porous cultures into fixed categories. This tragic "lie of the colonial situation", as Frantz Fanon called it, rebounds on us tragically in the terror unleashed in the name of Islam and Bush's "war on terror". If we are to undo the destructive legacies of empire, it won't do to invest celebratory falsifications with credibility. To make sense of a shared present and look towards a more humane future, we need to start with a little informed honesty about the past.

· Priyamvada Gopal teaches postcolonial studies at Cambridge University and is the author of Literary Radicalism in India: Gender, Nation and the Transition to Independence

pg268@cam.ac.uk