The viability of the human race is at stake because of "offences against our environment" which threaten the world with further wars and rising inequality, the Archbishop of Canterbury, Dr Rowan Williams, said last night.
He warned that in the short term the "addiction" of rich nations to fossil fuels had all the ingredients for the most "vicious kinds of global conflict - conflict now ever more likely to be intensified by the tensions around religious and cultural questions".
He forecast the emergence of "fortress societies" able to possess all the natural resources such as oil and water they required, with the rest of the human race excluded.
In his first "green" speech as archbishop, Dr Williams adopted the approach of the Eastern Orthodox Church that destroying the environment was a sin, and that Christians had a duty to protect it.
He said: "We should be able to see that offences against our environment are literally not sustainable. The argument about ecology has advanced from concerns about 'conservation'. What we now have to confront is that it is also our own 'conservation', our viability as a species, that is finally at stake."
He endorsed the remark made by Sir David King, the government's chief scientist, describing climate change as a "weapon of mass destruction", and called on Tony Blair's government to take a lead in sharing the earth's resources to avoid inequality and conflict over oil and water resources.
While the long-term threat was to the survival of the human race, in "the shorter term, what is at stake is our continuance as a species capable of some universal justice".
Dr Williams criticised a society "in denial" about the destruction of the environment. As an example, he used current economic thinking which did not regard environmental factors such as soil degradation, deforestation and a disrupted food chain as costs of economic activity.
In the speech at Lambeth Palace, he said that since "the oil production of relatively stable and prosperous societies is fast diminishing, these countries will become more and more dependent on the production of poorer and less stable nations.
"How supplies are to be secured at existing levels becomes a grave political and moral question for the wealthier states, and a destabiliser of international relations.
"This is a situation with all the ingredients for the most vicious kinds of global conflict."
Dr Williams said that if human beings are not to be living in prolonged and suicidal conflict with the natural order tough choices must be faced.
He backed a plan by the Global Commons Institute for fair shares of fossil fuel use between countries known as "contraction and convergence". This involves every person on the planet having an equal right and quota to emit carbon dioxide.
He explained that in the first 48 hours of 2004, an average American family would have been responsible for as many emissions as an average Tanzanian family over the year.
Dr Williams appealed to Tony Blair to use the coming chairmanship of the G8 group of industrialised countries and the presidency of the EU to press the environmental case. "The prime minister has already declared that his international priorities for 2005 will include climate change and the future of Africa; contraction and convergence addresses both of these. It seems the moment to look for a new level of public seriousness about environmental issues."