Green Party chairman Mr John Gormley has claimed any agreement reached at the Earth Summit would fall far short of what is required to make the planet truly sustainable.
Mr Gormley, who is part of the Irish delegation in Johannesburg, said it was likely that some form of agreement would be reached but the compromises will make any agreement "pretty weak in the context of what the human race needs to survive."
"If each country, or particular trading blocs, continue to safeguard their own trade interests into the future, the consequences will be devastating. Ultimately, the plain truth - that we cannot have infinite economic growth on a finite planet - does not seem to have dawned on the nations of the world," he said.
Mr Gormley is expected to address the Inter Parliamentary Union meeting at the summit tomorrow.