The Bishop of London, the Right Reverend Richard Chartres, said that the purchase of large cars or even holiday flights was an environmentally "selfish choice". But Edmund King, executive director of the RAC Foundation, said decisions over what car to buy were "practical" and not moral choices.

The bishop, who has helped form Church of England policy on the environment, said there was now an "overriding imperative" to "walk more lightly upon the earth". He said people had to make lifestyle decisions with environmental consequences in mind. "Making selfish choices such as flying on holiday or buying a large car are a symptom of sin," he told the Sunday Times. "Sin is not just a restricted list of moral mistakes. It is living a life turned in on itself where people ignore the consequences of their actions."

Mr King said: "You cannot just point the finger in that way. Some people have larger cars for perfectly legitimate reasons, so I don't think morality comes into it. Yes, climate change is a problem, but we need an overall strategy to tackle it. This is rather a knee-jerk reaction from the Church, maybe they should stick to what they know best."

The comments from the Bishop of London come ahead of the publication of a Church booklet advising Christians on practical action towards being more eco-friendly. The bishop also recently led the launch of the Church's Shrinking the Footprint scheme aiming to cut the "carbon imprint" caused by inefficient energy use in its own buildings.

Mr King said yesterday: "I don't think it is particularly helpful to have such gross generalisations."

A spokesman for Mr Chartres said: "What we are trying to do is to put our own house in order first."