The British-born former AIG chief executive Martin Sullivan drew derision from US politicians by admitting he knew virtually nothing about the insurance company's vast exposure to complex financial insurance products until the credit crunch sparked early signs of a meltdown at the near bankrupt firm.

A US inquiry panel investigating the financial crisis quizzed Sullivan and several fellow former AIG bosses including Joseph Cassano, who ran the firm's financial products arm in London, about the collapse of AIG in 2008 that culminated in a government bailout costing $182bn. Its problems have been pinned on ill-fated derivatives contracts of more than $1tn.

There was little in the way of apology from the executives. Sullivan, a lifelong AIG employee who was once lauded as Britain's most influential businessman in the US, delivered a shoulder-shrugging performance in which he said he was unaware of crucial contractual terms in AIG's financial products until the middle of 2007, when Goldman Sachs began making multibillion dollar collateral calls on the firm. "I only became aware of the CDS [credit default swap] portfolio in 2007," said Sullivan. "I was receiving reports, but they didn't indicate any problems with the portfolio."

AIG has been described by critics as a large, stable insurance firm dwarfed by a huge "hedge fund" in the shape of its financial products division. The unit, run out of an office in Mayfair, wrote contracts insuring financial institutions against default by counterparties. AIG was plunged into chaos when banks began making billions of dollars of collateral calls. The first of these calls came in July 2007, when Goldman Sachs asked for $1.8bn. Sullivan, who was then the boss of AIG, admitted he did not know about Goldman's demand until after the event. "It was weeks or months later," said Sullivan, asked when he became aware of the problem. "It was nowhere near around July time – I think it was much later on in the year."

This was greeted with amazement by Bill Thomas, vice-chairman of the US financial crisis inquiry commission, who said: "I will admit I've never been involved in an enormous multinational operation [but] there's not much communication in what I'd have thought was a major problem in a significant sector of the business."

The implosion of AIG, which came a week after Lehman Brothers' bankruptcy, was described by the Federal Reserve chairman Ben Bernanke as the most anger-inducing moment of the financial crisis.

Sullivan, who was appointed OBE three years ago, has been attacked for being asleep at the wheel and is the latest British executive, following BP's Tony Hayward, to feel the wrath of US politicians.