Up to 300 oilmen at the GO-EXPO in Calgary, Canada witnessed an unusual presentation about turning human flesh into fuel by 'representatives of Exxon and the National Petroleum Council (NPC).'

The two 'representatives' turned out to be pranksters from the civil disobedience group The Yes Men.

Conference organisers billed the speech by a 'NPC rep' as a major highlight.

The real NPC, which is headed by former ExxonMobil CEO Lee Raymond, regularly consults with the White House on energy policy.

The 'NPC rep' was expected to present findings from a long-awaited study chaired by Mr Raymond in conjunction with the US Department of Energy.

The fake speech, delivered by 'Shepard Wolff' (aka Andy Bichlbaum of the Yes Men), unveiled a new Exxon oil product called Vivoleum.

'We need something like whales, but infinitely more abundant', said 'Mr Wolff' as he showed 3D animations of human flesh being rendered into the fuel.

'Vivoleum works in perfect synergy with the continued expansion of fossil fuel production', noted 'Exxon rep Florian Osenberg' (aka Yes Man Mike Bonanno).

He added: 'With more fossil fuels comes a greater chance of

disaster, but that means more feedstock for Vivoleum. Fuel will

continue to flow for those of us left.'

The Yes men also lit 'commemorative candles' in honour of an 'Exxon janitor' who died as a result of cleaning up a

toxic spill.

The audience started to realise the prank when the janitor, in a video tribute, announced that he wished to be transformed into candles after his death.

The two Yes Men were then removed from the stage, but stayed in character when interviewed by journalists outside.

They were not charged by police after officers determined no major infractions had been committed.