The world's finest diplomats will spend weeks drafting and redrafting the communiqué that will be issued at the end of the Group of 20 summit in London next week. But why do they bother?

To understand the emptiness of the exercise, you need only look back at the communiqué issued after the G20's first summit in Washington last November. The leaders solemnly declared: “We underscore the critical importance of rejecting protectionism … We will refrain from raising new barriers to investment or to trade in goods and services.” To emphasise their determination, they “instructed” their trade ministers to complete the Doha round of trade negotiations by the end of 2008.

And what has happened since then? Naturally, the Doha round has not been completed – not even close. In fact, a World Bank study issued last week showed that 17 of the countries that signed up to the G20's Washington declaration have since taken protectionist measures.