T. Rowe Price Group Inc. said May 6 it intends to vote against the Occidental Petroleum Corp. board of directors because the company will not allow shareholders to vote on its bid for Anadarko Petroleum Corp., which T. Rowe Price and other shareholders oppose.

Several other investors also said they might vote against approving Occidental's board of directors at the annual meeting on May 10. Occidental on May 5 increased the cash component of its $38 billion bid to acquire Anadarko, removing a requirement for Occidental shareholders to approve the deal.

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That move led Anadarko on May 6 to name Occidental's $76-a-share offer as superior to that submitted by Chevron Corp., requiring Chevron by May 10 to revise its offer or walk away.

"We don’t feel we have any choice," said fund manager John Linehan, portfolio manager at T. Rowe Price. "We really struggle to understand the logic of not putting a transformational deal to your shareholder base."

T. Rowe Price, Occidental’s sixth largest shareholder, held 21.1 million shares of the oil company as of Dec. 31, along with 865,000 shares of Anadarko and 8 million in Chevron, which offered $33 billion for Anadarko.

Occidental risks the ire of billionaire activist Carl Icahn, who has been amassing a stake in the Houston-based oil producer intending to challenge its Anadarko offer, according to sources.

Icahn's involvement throws a wild card into the merger battle, said David Katz, president of Matrix Asset Advisors, which held 241,700 shares of Occidental and 61,300 shares of Chevron at the end of April.

Matrix opposes the merger and may vote against the Occidental board "to send a message," Katz said. "We don’t think they’re correctly handling their fiduciary decisions."

Occidental CEO Vicki Hollub said May 6 the decision to increase the cash portion of the offer was designed to address Anadarko's need for greater certainty the deal would go ahead.

"Our objective in doing this was not at all to avoid a shareholder vote. It was to ensure we had a reasonable chance to make this happen," she said on a conference call on May 6. "We weren’t at all on a level playing field," she said, noting that the Anadarko board had failed for days to make a decision.

It has "been a 12-day process" and "our proposal still wasn't deemed superior, which is why we've yesterday submitted the increased cash offer," Hollub said.

Occidental's bid includes a pricey financing deal with billionaire Warren Buffett, whose Berkshire Hathaway Inc. would receive preferred shares paying an 8% dividend.

"Occidental putting in more cash is really a ploy to not have a shareholder vote," said Christian Ledoux, investment chief at South Texas Money Management, which holds shares of Chevron and Occidental. "That’s upsetting from an investor point of view."

Ledoux opposes the merger, fearing that Occidental would go into the next oil price downturn with a debt-laden balance sheet. He has not decided how his company will vote on the Occidental proxy. It will wait to see what else develops and whether Icahn takes a stand, Ledoux said.

"I would imagine there’s going to be a lot of votes against [the board] as a protest," Ledoux said.