On the basis of the text of the G20 summit communiqué, leaked comprehensively yesterday, it seems pretty clear that the event will be a flop. But could Thursday's G20 Summit do more harm than good?

Yes. The text indicates that little concrete will be agreed beyond extra resources for the IMF – worthy, but it could be achieved without pulling 20 exceptionally busy leaders together for a group photo.

President Obama, Gordon Brown, the German Chancellor Angela Merkel and disparate others – from Argentina to Indonesia via Saudi Arabia – are set to sign up to a communiqué that commits them to "the measures necessary". Sadly that "rough consensus", as Mr Obama describes it, includes doing nothing, a policy that will continue to be followed by the Germans, French, Italians, even the Chileans – and the British, too, embarrassingly for Mr Brown, if the Bank of England governor really has vetoed another big fiscal boost in the 22 April Budget.

This Thursday's summit will, unhelpfully, highlight discord. The stock markets won't crash – most long ago wrote off the G20 as a media circus, their disappointment already "priced in". But something far worse than the status quo may emerge.

Why? Because, just as the Soviet Union proved that you cannot have socialism in one country, so will the summit reveal how you cannot have reflation in one country. Look at it from the point of view of the US. Put bluntly, why should America agree to buy new German cars and French wine if Merkel and Nicolas Sarkozy won't agree buy American goods in return? The cry will go up in the most protectionist Congress in 60 years – as it has already, but it will become shriller – that taxpayers' dollars should be used to "Buy American". Hey presto, the G20 summit helps roll the world economic machine backwards towards "beggar my neighbour" polices.

Ah, but doesn't the summit communiqué say that the G20 "reaffirm the commitment made in Washington not to raise new barriers to investment or to trade in goods and services"? Sure. But then the World Bank says that since the November G20 summit, 17 out of the 20 nations have implemented protectionist measures. This summit may "name and shame" the miscreants into better behaviour, but it seems unlikely.

The summit could turn ugly. The Americans and Japanese may wonder aloud why they run risks with their balance of payments, the dollar and yen, and future inflation. Interviews with Merkel and Sarkozy will draw attention to their indifference to such concerns. The Brazilians may declare that the failure of the summit is down to white men with blue eyes. The Chinese could, damagingly, talk about their worries about the dollar. The Saudis might join in. The South Koreans will scream about trade barriers. The Russians will sulk. A global crisis will bring forth not global solutions but the biggest global custard pie fight since Mack Sennett. Forget those rioting protesters outside.

Mr Brown may well wonder why he bothered.