Mellon Bank Corp.'s decision to reject Bank of New York Co.'s unsolicited bid is making some of its activist shareholders impatient.

On Tuesday, Guy P. Wyser-Pratte, president of the eponymous New York investment firm that owns 100,000 Mellon shares, released a letter to Mellon chairman Frank V. Cahouet chastising him as showing "no sign of being willing to allow shareholders to make a fully informed decision on the Bank of New York offer."

"I am deeply disappointed by the board's initial handling of the Bank of New York proposal," Mr. Wyser-Pratte wrote. "The board should be giving shareholders all the facts and, at the very least, conducting a shareholder referendum on the Bank of New York offer." He suggested he would increase his Mellon stake and "institute the necessary procedures" for a referendum.

Mellon declined to comment on the letter. However, the bank issued a statement saying that it believes its shareholders "will understand the facts and continue to respect the judgment of the Mellon board."

Mr. Wyser-Pratte is known for rattling American corporate cages. Earlier this month he settled a dispute with Pennzoil Co., which emerged from the company's decision to reject an offer to sell for $84 per share.

Mr. Wyser-Pratte attempted to join Pennzoil's board, and the company decided to cut its board by one member rather than let him on. But on April 3, Pennzoil agreed to hire one independent director to be selected by the company with the approval of its big shareholders, including Mr. Wyser- Pratte.

Subscribe Now

Access to authoritative analysis and perspective and our data-driven report series.

14-Day Free Trial

No credit card required. Complete access to articles, breaking news and industry data.