"Unless developed countries are willing to give more than they get, and offer real development dividends, there is a high risk that developing countries will walk away," McKinnon told a meeting of the Commonwealth People's Forum ahead of a 53-state summit here this week.

"They have already done so, as you'll recall at Cancun (the failed Mexico talks in 2003) and they'll do so again. For them, no deal is better than a bad deal, and I have a great deal of sympathy for that," the body's general secretary said.

Signalling a get-tough stance from smaller states which comprise a large part of the loose association of former British colonies, McKinnon said this weekend's summit should drive forward the political agenda and "pursue a higher level of ambition."

He said there was now "a high level of despondency and a low level of ambition for the Doha Round. The negotiations are in more serious trouble than ever before."

"But developing countries did not get a deal on agriculture in the Uruguay Round. We said at the end of the round that we would attend to developing country needs and to agriculture next time. Now is the next time."

"If heads this weekend can come out with a clear political message to their negotiating teams to maintain a high level of ambition, then our 53 leaders may be able to give the WTO the shot in the arm it requires at this critical moment."

"We account in the Commonwealth for one fifth of global trade, so we have a legitimate right and a responsibility to show leadership."