It will take some time, perhaps a generation, for the full impact of the WikiLeaks disclosure of thousands of US diplomatic cables to become known. For this is an event of historic importance for all governments, not only the US. While they may roar their condemnation, governments are also pretending that it's business as usual. But what we have witnessed is something very dramatic in the world of diplomacy - and thus in the way that the world runs its business. We may now date the history of world politics as pre- or post-WikiLeaks.

The press may have concentrated on Gaddafi's voluptuous nurse or Karzai's corruption (which is depicted in excruciating detail in the cables), but this event carries a much deeper significance than merely the highly embarrassing and, in some cases, destabilising revelations in the enormous hoard of documents. Neither the US State Department nor WikiLeaks can say with any confidence whether the effects of this release will be good or bad, for in truth neither of them can know. There will be manifold and long-lasting consequences; that is all we can know for sure.

Word and deed

The presumption that governments can conduct their business with one another in secret, away from the prying eyes of the public, died when the leaks started to emerge on 28 November. Diplomats and officials around the world are now realising that anything they say may hit the public sphere - ie, the internet. Governments are no doubt rushing to secure their data and hold it more tightly than ever, but it's too late. If a government as professional, technologically sophisticated and well-protected as the US can suffer a breach of this magnitude, no other is safe. Politicians can demand the prosecution of Julian Assange or - absurdly - that WikiLeaks should be designated as a terrorist organisation, but the rage is a tacit admission that a government's monopoly on its own information is now a thing of the past.

Hillary Clinton has described the WikiLeaks disclosures as an attack on the "international community". But they are something else: an ­attack on the governments that make up the current international system of diplomacy. The cultural and political assumption that governments have business that they should conduct in secret with one another has taken a massive hit. From now on, it will be ever more difficult for governments to claim one thing and do ­another. For in making such claims, they are ­making themselves vulnerable to WikiLeaks of their own.

Why? Because the most embarrassing thing about the WikiLeaks disclosures is not that they happened (though this is bad enough for the American government), but the revelation - long suspected but now proven - of the yawning discrepancy between US words and actions in that most contested area, the Middle East. Cable after cable details the extraordinarily intimate and codependent relations between the US and various despotic and unpleasant Arab regimes. One Arab intelligence chief plots with the Americans to target Iranian groups, or destroy Hamas. Another undemocratic Arab leader invites US bombers to attack targets in his own territory. It is this discrepancy - between word and deed - that will keep fuel in WikiLeaks's tanks and those of others like it.

Governments around the world are convincing themselves that nothing has changed and that if they restrict the circulation of those really sensitive telegrams and glue up the USB slots in their computers, this won't happen to them. But it will. There will be more such ­revelations, not just about the US (which has so far been the main target of WikiLeaks's somewhat arbitrary attentions), but others - Britain, China, perhaps - the reality is that electronic data is formidably difficult to protect. The reason is simple. To be effective as organisations, governments and foreign offices are required to circulate sensitive data, so that their officials and diplomats know what's going on.

One reason the UN Secretariat is ineffective is because nothing is secret there, so no one circulates anything sensitive. Don't buy the argument that the really important stuff is kept "Top Secret" and hasn't been compromised. Even a cursory perusal of the WikiLeaks store reveals cables that are the very meat and drink of diplomacy - what foreign leaders and governments really think and want in their relations with the US.

WikiLeaks mission

Thus, governments are confronted with a conundrum. If they restrict and protect the data, and perhaps even stop recording the most delicate information (as no doubt some diplomats are now considering), they will inevitably reduce their operational effectiveness. If they circulate the data widely, as the US did pre-WikiLeaks, they will risk compromise on this devastating scale.

There is only one enduring solution to the WikiLeaks problem - and this is perhaps what Assange wants, if one can get past his rather confusing statements - which is that governments must close the divide between what they say and what they do. It is this divide that provokes WikiLeaks; it is this divide that will provide ample embarrassment for future leakers to exploit. The only way for governments to save their credibility is at last to do what they say, and vice versa, with the assumption that nothing they do will remain ­secret for long.

The implications of this shift are profound and, indeed, historic.

Carne Ross resigned from the Foreign Office over the Iraq war. He founded and now runs Independent Diplomat, the world's first non-profit diplomatic advisory group. He is also the author of "Independent Diplomat: Dispatches from an Unaccountable Elite" (Hurst, 2007)