The world's oil reserves are running out much faster than industry and governments are admitting, a conference in Edinburgh has been told.
Experts refer to "peak oil", the time when oil extraction reaches its highest point and then starts to decline.
Many industry experts believe it will not occur until 2030 - but some analysts have stated publicly that it could happen by 2008 or even sooner.
About 200 people from various sectors attended the event.
Dr Jeremy Leggett, a member of the UK government's Renewables Advisory Board, predicted: "Most of us who are worried about this issue would say definitely it will happen some time this decade.
"2008 might be the best guess, plus or minus two years. It's certainly a lot earlier than almost all the world is assuming at the moment.
"Oil reserves in many countries are state secrets. The biggest oil companies in the world are owned by governments.
"They have no requirement to report. There are many worrying indications that things they have been reporting are inaccurate."
Dr Leggett, a former oil geologist and Greenpeace campaigner, went on: "Modern life depends on growing supplies of cheap oil and the world economy is predicated on the assumption that that is going to continue for another couple of decades and it is not.
"There is going to be a profound economic shock and we will not be able to bring in renewable energy in time to repair the damage.
"It's just not on radar screens. It's difficult to find people talking about it anywhere. I find it very bewildering because I think the evidence is clear on this one.
"We need to take this issue as seriously as we take the war on terrorism - more so.
"It's much more dangerous, much more of a threat to our economic well-being. We need to rush through programmes to get alternative fields to save energy."
'Ripe for review'
Delegates to the conference, organised by Depletion Scotland and the Oil Depletion Analysis Centre (ODAC), also heard from ex-energy minister and former MP for Cunninghame North, Brian Wilson.
He said that Britain's current energy policy was "ripe for review" and should be a major issue in the election campaign.
Mr Wilson, who is not standing as an election candidate, said the UK was set to become a net importer of oil and gas in the next few years.
He called for a balanced and indigenous energy future for Britain, embracing energy alternatives as well as conservation.
But Mr Wilson said the biggest global challenge in energy terms was persuading the United States to reduce its own oil consumption.
He attacked America's "ever-increasing and ever-more profligate application."