The US and British regulators launched inquiries after Shell admitted in January it had overstated its proved oil and gas reserves, which it has since cut by a total of 4.47 billion barrels, or 23 per cent. According to the SEC order, Shell also inflated the standardised measure of future cash flows reported in the 2002 filing by about $US6.6 billion ($A9.3 billion). The company corrected the figures for reserves from 1997 to 2002 in an amended filing on July 2 of this year. "Shell's overstatements of its oil reserves, which occurred over an extended period, mandate a strong enforcement response, including imposition of significant civil penalties, to deter Shell and others from engaging in similar misconduct," SEC administrator Harold Degenhardt said in a statement. "As our investigation continues, we intend to focus on, among other things, the people responsible for Shell's failures."