Christophe de Margerie, Total’s chief executive, has been warning for more than a year that political hurdles such as sanctions meant the world would not be able to produce more than 95m barrels a day of crude oil.

But as the credit crunch delays expensive projects and lower oil prices dissuade oil-rich nations from investing in tapping more of their riches, oil executives are privately warning that even 95m barrels could prove optimistic.