MADISON, WIS. -- The Rev. Gordon MacDonald, 47, an evangelical author and lecturer, resigned the presidency of InterVarsity Christian Fellowship after confessing that he was "involved in an adulterous relationship in late 1984 and early 1985."

He and his wife Gail made the announcement to the InterVarsity board at its regularly scheduled meeting in Madison on June 5.

The MacDonalds will celebrate their 26th wedding anniversary in August.

"Gail and I would wish this board and our companions in ministry to know how sorry we are that we have so badly hurt the Lord and his people," MacDonald said at the meeting. "I need your forgiveness."

MacDonald said he "had hoped for a long period that, having taken all the biblically defined steps that call for confession, repentance and restoration, the tragedy in my past would have been over and buried. But when rumors about this matter began to circulate in the past weeks, I knew that I must withdraw from InterVarsity's leadership for the best interests of a great organization."

The resignation and the reason for it were made public by InterVarsity in a news release.

The woman's name was not made public.

In his statement to the InterVarsity board, MacDonald said, "Our own marriage relationship is solid and growing today. We will continue to try to be faithful to everything we've ever written or spoken in public in spite of the fact of this failure in the past. We have no plans for the future at this time except to enter into an extended period of quiet before the Lord."