Rebel Hewlett-Packard (HP) board member Walter Hewlett may sell off HP shares under his control if the firm completes its proposed $22bn merger with Compaq.
Hewlett has a personal stake of under one per cent in the company, but is chairman of the Hewlett Foundation.
He said the foundation, a charitable organisation, is also likely to sell its 1.9 per cent HP stake if the merger is approved at a shareholder vote on 19 March.
He said negative market reaction to an approved merger could leave the charity more than $550m out of pocket.
The Packard Foundation, which owns 10.4 per cent of HP, is also opposed to the deal.
Critics of the merger say it is an unnecessary risk for HP, which would be exposed to Compaq's commodity computing business.
Next week, proxy advisory firm Institutional Shareholder Services (ISS) will either recommend or oppose the merger to its clients, a decision analysts believe could decide its outcome.
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