NEW YORK – Nearly half of the board members of Williams Cos. quit this week after they unsuccessfully tried to force out the energy company’s CEO.

In a letter made public Friday, former board member Eric Mandelblatt says he and five others quit Thursday after the remaining board members were unwilling to push out CEO Alan Armstrong. Mandelblatt said Armstrong is “incapable” of increasing shareholder value and “lacks the necessary judgment and character” needed to lead the company after a failed $33 billion takeover bid from rival Energy Transfer Equity.

In a statement, the company said Armstrong is the right leader for the Tulsa, Oklahoma, company.

Among those who left the board was former Chairman Frank MacInnis. The company named Kathleen Cooper as his replacement, bringing its total members to eight. Before the six members quit, the board had 13 members.

The others that left were Ralph Izzo, Keith Meister, Steven Nance and Laura Sugg.

In his own letter, Meister said the remaining members who refused to replace Armstrong were acting out of a “personal loyalty” to Armstrong instead of “permitting the facts of his performance to take them to the correct answer.”

Energy Transfer Equity called off its deal to buy Williams Cos. on Wednesday, after lawyers couldn’t deliver an opinion on the how the deal’s taxes would be handled. Williams said Energy Transfer Equity breached the deal agreement and would seek “monetary damages.”

Shares of Williams Cos. fell $1.24, or 6 percent, to $20.39 in afternoon trading Friday.