Xerox's aspirations to buy much-larger HP are not over yet, with Carl Icahn urging HP shareholders to back the $US33.5 billion bid.

Icahn says he is the largest individual shareholder in both companies with 10.85 per cent of Xerox Corporation and 4.24 per cent of HP.

He accuses to engage in mutual due diligence processes, and suggests individual interests may be at stake. "Over the last several decades as an activist I have made billions and billions of dollars not only for Icahn Enterprises but for all shareholders by standing up to managements and boards that have refused to do anything that would change the status quo, which might mean threatening their huge incomes," he says.

"I cannot believe that the recalcitrance of HP's board is driven by any real confidence in its standalone restructuring plan, which the market, shareholders and analysts met with extreme indifference and which seems to amount to little more than rearranging the deck chairs on the Titanic."

Xerox Corporation's unsolicited offer of $US33.5 billion on November 5 was refused - with HP chairman Chip Bergh citing Xerox's declining revenue and "future business trajectory" as reasons - and then followed up with an appeal to directors to reconsider.

The letter argued the logic of combining the businesses would accelerate the transformation and create a leader in emerging growth markets.