Tough spot, but not unusual. There are a few approaches, depending on the political climate/culture.
1) Talk with your peers and explore the option of a 'confrontation' meeting - better if scheduled as something informal, a private dinner or lunch together, some pre-meeting coaching re: diplomacy and developing a strategy to broach the topic and surface the issue would likely be helpful;
2) If he has one or more close/trusted advisers you are aware of (within the company or circle of friends/colleagues), gaining their assistance to broach the subject with him can be effective to bring him to the table with the team productively, but needs to be planned well so no one executive team member is put in a position of shouldering responsibility for the intervention;
3) Get the executive team together to request a one day, facilitated offsite to assess the business, how the leadership team functions as a leadership body and what needs to happen to optimally guide the company successfully forward. The design of the meeting would be based on interviews with executive team members and the consultant/facilitator would serve as diplomat and facilitator - coaching the leader going into the meeting and managing the dialogue so that this issue is put into a larger strategic context (versus being the whole picture/focus). (I've seen the greatest success with this last option). The consultant/facilitator needs to be highly experienced to design/manage this well (experience in strategic planning, leadership development, diplomacy and mediation).