Don't blame us, blame the rules. Oh yes, and the evil short sellers who attacked our share price. That was the main thrust of the excuses from former AIG chief executives today in their statements to Congressmen in Washington.

Former chief executives Robert Willumstad and Martin Sullivan said the accounting rules in the US, which require companies to value securities at current prices even in distressed situations like the credit crunch, were the cause of its downfall.

The bonds AIG had insured fell so much in the credit crunch that the insurer had to write off billions of dollars to reflect the theoretical loss it would suffer if those bonds were all sold immediately. "Mark-to-market" accounting has long been seen as a cause of the current crisis.

House Oversight and Government Reform Committee chairman Henry Waxman countered that Sullivan had assured investors on 5 December 2007 that AIG was happy with its writedown levels even though accountant PwC had warned a week earlier that it was concerned about the numbers.