Abbot Christopher Jamison, star of the BBC television series The Monastery, has warned that rampant consumer culture is taking over people's moral purpose, and must be tackled in order to address climate change.
He urged people to enjoy the month of Advent rather than celebrating Christmas early, but also that climate change can not be answered purely by science and technology, and needs to be understood as a moral and spiritual issue.
The Abbot of Worth School blamed the current economic crisis on a "lethal combination" of lack of ethics and an excess of regulation in the world of finance.
He also said that rules and laws would not be enough, any more than they were enough to curtail the worst excesses of the City, to deal with climate change.
In a lecture at London's St Alban the Martyr church to coincide with a new "Reclaim Christmas" campaign by Operation Noah, Abbot Jamison said: "Our Western culture is saturated with goods.
"The economically stable individuals and households who make up the majority of our population have more stuff than they actually need.
"While they might be persuaded to buy some more or different versions of what they already have, business recognises this material saturation and so the present thrust of consumerism is towards selling culture as well as things.
"Having saturated the world of our material needs, consumerism is now taking over our need for cultural goods such as music, entertainment and even moral purpose."
He cited the example of a section of Nike's website, called 'Addicts Gallery', in which runners talk about sport as their "higher purpose".
"Even our souls are now consumerised and marketing is taking over not only our material imagination but also our spiritual imagination," the Abbot said.
"So Nike and the other great corporations now inhabit our imagination, the place where greed is generated. Once planted there they can make us endlessly greedy. And that is exactly what they are doing."
He denounced the "shopping frenzy" of the run-up to Christmas, followed by one day of peace and goodwill "then looking forward to the sales", and encouraged people to celebrate "temperance" during Advent.
The Abbot also told how he was once involved in a project to promote ethical training among bankers that the Financial Services Authority, the UK's City watchdog, commissioned but later ditched.
"The ethical project was over, the window of opportunity was closed and five years later the consequences are clear. While there are many proximate causes of the current financial crisis, the ultimate cause is ethical," he said.
"We can now see that the financial services industry was both over-regulated and unethical, a lethal combination, like a school with strict teachers where amazingly the pupils still get away with murder."
He also called for a new "ethics project", similar to the development of human rights in recent decades, to safeguard the environment.
"It’s not just a question of finding techniques that can prevent environmental harms, even if it’s important to find alternative sources of energy and so on" he said. "But all this won’t be enough if we ourselves don’t find a new style of life, a discipline which is made up in part of renunciations: a discipline of recognition of others, to whom Creation belongs just as much as those of us who can make use of it more easily; a discipline of responsibility to the future for others and for ourselves."