It's not only the concept of humanitarian intervention that has been fatally undermined by the decade of Bush and Blair. It is the whole ideal of promoting democracy abroad. Not that either the White House or Whitehall have given up on the rhetoric. Indeed, President Bush still goes on about America's historic role in promoting democracy around the world. It was the one single theme that he picked up from the neo-cons at the beginning of his administration and has hammered on about ever since.

And now he's been joined by our own Foreign Secretary, David Miliband, who, in a speech on Tuesday night, reiterated at length why democracy was the key theme of British foreign policy.

US presidents tend to present democracy – and have done so ever since the days of Woodrow Wilson – as a unique gift of America, an ideal which all people aspire to but which "realpolitik" European colonial powers have tended to obstruct with pragmatic talk of interests and stability. Interestingly, Miliband has now resorted to exactly the same rhetoric, rejecting the criticism of those who doubt the West's right to impose ways of government on other nations as somehow denying the rights of people to enjoy the same degree of and freedom that we enjoy.

But that is a false dichotomy. The problem of pushing a system of government as a universal value, as Bush and Miliband assert, is not that the value is wrong or should not be supported. That is what we believe in, that is what we should stand by in our dealings internationally. It is that western demands on governments, of whatever hue, to sign up to a list of democratic tick boxes as the price of aid, support or whatever, have proved largely self-defeating.

In the first place, they have laid Britain and America open to an endless charge of hypocrisy. We have said that elected leaders must be supported, and then promptly sought to crush the forces of Hamas voted in by the Palestinians. We have urged democracy on the Middle East, only to prostrate ourselves before Saudi Arabia. We have condemned Iran, but made that most oppressive of regimes in Libya our golden boy because it has given up on its nuclear ambitions. We lecture Burma, but pussyfoot on the subject of human rights with China

Even more damaging to our cause, however, has been the recent experience of democracy in so many countries. We may talk of democracy as a set of values; to most of the world it is a mechanism of power. And over the last decade – in Thailand, Pakistan. Kenya, Uzbekistan, Kyrgestan, Georgia, Zimbabwe and a host of other nations – the resort to the vote has been simply a means of sustaining tribes or tyrants in power.

In a devastating review published a fortnight ago, Human Rights Watch concluded that "by allowing autocrats to pose as democrats, without demanding they uphold the civil and political rights that make democracy meaningful, the United States, the European Union and other influential democracies risk undermining human rights worldwide".

They are quite right. Instead of a tool for improving the lot of their people, reconciling tribal and minority interests and upholding the rule of law, the resort to the ballot box has become a means of doing the opposite, imposing the power of one tribe on the rest, pushing aside the law and oppressing minorities.

David Miliband is not wrong in pressing for a foreign policy that puts democracy as a goal profoundly worthy of aspiration. The trouble with western intervention, however, is that, as democracy concerns power, outside pressure too easily becomes a part of that power. The abuse of power in Kenya, Pakistan and Nigeria would not have happened if we, and the aid agencies, had not supported our favoured candidates in the belief that we could influence them on the "road to democracy".

David Miliband's suggestion that the UN, and the EU, should guarantee the security of nations after a "popular vote" would only make that worse, not better. Who after all is to judge what is genuinely democratic and what is gerrymandered? We should have learnt from Russia, as Pakistan this month, how fraught a question that is.

If I were the new Foreign Secretary, I would drop the word democracy altogether. It is in danger of becoming too devalued as a concept. Concentrate instead, in our discussions with China, the Gulf States and Africa, on the things that make up democracy: freedom of speech, an independent judiciary and equal human rights for all. On those we can talk with some (although not complete) authority and may hope to make some difference, step by step.