Robert Pittman has quit as chief operating officer of AOL Time Warner, as the company struggles to bed down after its mega-merger.
Bosses of two of the group's companies - Don Logan, head of Time Inc., and Jeffrey Bewkes, chairman of Home Box Office - have been given extended roles to bridge the gap.
Commentators have suggested that the two will take a more hardline approach than Pittman to combat AOL's problems.
Richard Parsons, chief executive at AOL Time Warner, said its divisions would operate "independently, but compete collectively".
The changes, together with concerns over accounting practices at AOL, saw another five per cent wiped off the firm's shares, which have dropped 60 per cent since the start of the year.
According to reports in the Washington Post, AOL bartered ads for computer equipment and counted stock rights as revenue in other deals.
But AOL's head of communications John Buckley insisted that the firm had done nothing that was not in accordance with generally accepted accounting principles.
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