UPDATE 1-Morocco's ONA conglomerate fires chairman

(Updates with more details)

RABAT, April 12 (Reuters) - ONA ONA.CS, a conglomerate that dominates Morocco's private sector, said on Saturday it has sacked its chairman Saad Bendidi, citing what it called serious management failings to develop its telecoms Wana venture.

Mouatassim Belghazi, who headed a ONA subsidiary, will replace Bendidi, it added in a statement released following a company's board emergency meeting on Friday.

Bendidi was not immediately available for comment.

ONA, which is controlled by the Moroccan royal family, has interests in banking, mining, food retail and agribusiness.

"ONA'S board notes that there is a noticeable gap between initial forecasts for Wana and the new ones which would result in additional investment of 5 billion dirhams ($688.3 million)," it said.

Blaming Bendidi for his failure to turn Wana into a profitable business, ONA added:

"It considers that, leaving aside the market parameters which were and still are favourable to develop a profitable third telecoms operator, this situation reflects serious management failings in planning and strategic direction of the enterprise."

ONA's board asked new chairman Belghazi, who headed Moroccco-Emirates Development Company which a ONA's affiliate, to come up with a new business plan for Wana and a project to upgrade the conglomerate's organisation after three months