Mr Meacher has already been upstaged. "We have high hopes but low expectations of the new government," said Peter Melchett, Greenpeace's UK director and himself a Labour peer who was a junior minister under old Labour. He was launching the group's dramatic new campaign to stop BP developing an oil field in the deep and stormy waters just west of Shetland. "A new frontier", BP calls it, and is looking forward to seeing oil come ashore this summer.

Greenpeace calls for a self-denying ordinance from the UK which would have the waters left as a frontier against oil development. It refuses to announce its plans for marine direct action, but high jinks on the high seas can clearly be expected. Combating Shell's dumping of Brent Spar was a huge coup; fighting to halt the new frontier is an irresistible successor.

The campaigners' logic is impeccable, as a new and brilliant little Greenpeace film will ram home in art cinemas shortly: "Within the earth is all the oil we need to set the world on fire," it trumpets.

Chris Rose, Greenpeace's deputy director and brightest policy wonk, insists that no industrialised country that takes global warming seriously should be increasing exploration, let alone exploitation, of its fossil fuel reserves. He proposes a phasing out of fossil fuel use within 40 years, and government rules insisting that most of the reserves remain underground. He says that is the only way to spare the world suffering a massive overload of climate-forcing gases.

Nearly everyone concedes that Greenpeace has the beginnings of a point, but hardly anyone takes them seriously. Peter Kassler, now working with the energy and environmental programme at the Royal Institute of Inernational Affairs, is an oil economist who used to be with Shell (which is a partner of BP's in the Atlantic frontier). Typically of the sceptics and the Department of Trade and Industry line, he says: "It's the sort of thing that has a facile appeal, but it's pretty thin. West of Shetlands oil at its best would be a marginal part of the world's oil supply. If that oil is demanded by consumers around the world it will come from somewhere else, without UK jobs and UK economic benefit. In 1997, the Middle East is relatively peaceful, but any sensible government would like to have flexibility."

But the toughest arguments Greenpeace must face come from people more obviously sympathetic to their cause, and even this campaign. Michael Grubb, a middle-of-the-road green, is putting the finishing touches to a paper which argues that governments are at risk of not noticing how relatively unimportant the world's oil and gas reserves are. "The amount of carbon in proven oil deposits is rather puny compared with the numbers the climate scientists play with." Greenpeace may say: fine, but there will be pressure to burn lots of coal, and it would at least help to lock up the oil and avoid the risk even more firmly. Dr Grubb suggests, rather, that the real goal would be to get the world to eschew the use of coal, which has a far greater capacity to do damage. That approach suggests that we need all the oil we can get as a replacement.

Greenpeace's game is one of alternating reasonableness and grandstanding. Cannily, Mr Rose's phase-out would give us longer to convert to non-fossil energy than the business-as-usual scenario, or even the regulatory framework now proposed. That is important: everyone agrees that, sooner or later, renewable energy and conservation must come into their own.

By far the most influential exponent of the "soft energy" path is the American Amory Lovins, who has a tropical climate at his mile-high, solar-powered Rocky Mountain Institute in Colorado, and whose latest co-authored book, Factor Four, declares that the world could have twice its present wealth for a halving of its energy take. That is because of the power of double-glazing ("the key to inexpensive buildings is expensive windows") and new engine and fuel technologies for vehicles, among myriad other developments in which, he says, root-and-branch changes in the way we design things will solve problems we knew we might solve, and others we didn't dare hope to cure.

"Oil is going to be rather abundant, and gas more so," he says, "but most reserves will stay in the ground because they are no longer worth burning." He believes that conventional fuels will get cheaper and cheaper but that renewables will overtake them and be cheaper yet. Moreover, he believes, the new wave of technologies will make renewables more convenient than conventional sources. Cars will become so clean that it will be their number, not their mess, which will pose the problem.

Even Lovins has some sympathy with the Greenpeace view, but only in so far as he thinks that it may be wise to maintain an oil reserve. Otherwise, there is little difference between the Lovins and the emerging industry points of view. Shell's group chief executive was praised by Michael Meacher yesterday for remarks stressing that his firm has now reached the "important point" when it's role as a good citizen requires it to work out the implications of being an energy company in a warming world. The campaigners have been less keen to point out that Mr Rothermund sees no contradiction between believing, as he does, that much oil may well stay in the ground because of falling demand and the viability of alternatives, and simultaneously wanting to get at the rich UK reserves in the eastern Atlantic. BP agrees very heartily, at least with the last bit of that.