SAN JOSE, Calif. — The bickering over the proposed $22.6 billion acquisition of Compaq Computer Corp. intensified Thursday as dissident Hewlett-Packard Co. board member Walter Hewlett asked the companies to scuttle the deal because of "enormous unhappiness" over the plans.

"The handwriting is on the wall and it is clear," Hewlett wrote to the boards of both companies in a letter filed Thursday with the Securities and Exchange Commission. "If the merger is brought forward for a vote, there is a very high probability that it will be defeated."

HP management said it took "major exception" to the letter and its claims of such widespread opposition. The company said in a statement that investors' and customers' concern over the deal mainly comes from Hewlett's own actions aimed at blocking it.

"It is an unsubtle attempt to prevent other shareholders from having their say, even before the proxy has been mailed," the company said.

Compaq's board also responded by telling Hewlett in a letter that it was confident shareholders of both companies would approve the deal.

Hewlett, the oldest son of HP co-founder William Hewlett, was the first of the Hewlett and Packard heirs to come out against the deal, saying it is too risky and likely would cut into HP's profits, especially by diluting the contribution of HP's printing division.

Since then, Packard family interests — including HP's largest shareholder, the Packard charitable foundation — also have lined up against the proposed acquisition. Overall, the opposition camp accounts for 18 percent of HP shares.

Walter Hewlett told the HP and Compaq boards it was "critically important" to relay what he has gleaned in his meetings with other large shareholders as he prepares for a proxy fight over the deal.

"There is enormous unhappiness about this transaction. This unhappiness goes far beyond those shareholders and analysts that have spoken out publicly," he wrote in the letter, which was dated Wednesday.

"If we simply continue to push forward to a shareholder vote, there will be serious and increasing adverse consequences. Each company will misdirect time and energy, waste money, suffer further degradation of employee morale, continue to confuse customers, and delay refocusing on the steps necessary to maintain and enhance itself as an independent company."

HP and Compaq believe that by merging they can become stronger in business computing, Internet access devices and high-tech services, and drive future industry trends rather than reacting to them.

The leaders of both companies reaffirmed their support for the deal this week, saying other shareholders are likely to study the transaction from different angles than charitable organizations such as the Packard Foundation.