Topeka-based Westar Industries announced Thursday it plans to sell all its shares of ONEOK, a Tulsa-based natural gas company.

Westar, which is subsidiary of Western Resources, owns about 44 percent of ONEOK’s stock. The announcement comes one day after Western officials made public a letter sent to the ONEOK board questioning the company’s senior leadership.

In the letter, filed with the Securities and Exchange Commission, the company said it had “little confidence” in ONEOK’s senior management to “formulate a business plan that makes economic sense for the company.”

The value of Western’s share in the company has been estimated at $980 million.

Under an agreement between ONEOK and Western, ONEOK has the right to purchase back Western’s shares in the company for $21.77 per share within 180 days.