In a letter that was read to the congregation of the New Life Church by another clergyman, Haggard apologized for his acts and requested forgiveness.
"I am so sorry for the circumstances that have caused shame and embarrassment for all of you," he said, adding that he had confused the situation by giving inconsistent remarks to reporters denying the scandal.
"The fact is I am guilty of sexual immorality. And I take responsibility for the entire problem. I am a deceiver and a liar. There's a part of my life that is so repulsive and dark that I have been warring against it for all of my adult life," he said.
Haggard resigned last week as president of the National Association of Evangelicals, where he held sway in Washington and condemned homosexuality, after a man claimed to have had drug-fueled homosexual trysts with him. Haggard also placed himself on administrative leave from the New Life Church, which has 14,000 members, but its independent Overseer Board fired him on Saturday.
In his letter, Haggard said "the accusations made against me are not all true but enough of them are that I was appropriately removed from his church leadership position."
He did not give details on which accusations were true.
The letter was read to the church by the Rev. Larry Stockstill, senior pastor of Bethany World Prayer Center in Baker, La., and a member of the board that fired Haggard. Youngsters were sent out of the room before elders began speaking about the church crisis.
"Worshippers are always challenged by crisis. And when tragedy and crisis strikes it is at that moment that you truly decide if you are a worshipper of the most high god. And today as the worship pastor of this church I am very proud of you," said the Rev. Ross Parsley, who has replaced Haggard.
"I am so grateful for the government system in place here at this church. ... The speed with which things were dealt with this week has been a testimony to the godliness, to the integrity and authority of the overseers of the board of this church," he said.
Haggard, 50, had acknowledged on Friday that he paid Mike Jones of Denver for a massage and for methamphetamine, but said he did not have sex with him and did not take the drug.
The Overseer Board, made up clergy from various churches, used stronger language.
"Our investigation and Pastor Haggard's public statements have proven without a doubt that he has committed sexually immoral conduct," the board said in a statement.
The NAE, representing 30 million evangelicals, named the Rev. Leith Anderson, senior pastor of Wooddale Church in Eden Prairie, Minn., as its interim president.
Jones said in a telephone interview Sunday: "I am sad for him and his family. I know this is a tough day for him also. I wish him well. I wish his family well. My intent was never to destroy his family. My intent was to expose a hypocrite.
"I hope the healing process can start. I welcome his request for forgiveness for me."
Haggard's situation is a disappointment to Christian conservatives, whom President Bush and other Republicans are courting heavily in the run-up to Tuesday's election.
Many were already disheartened with the president and the Republican-controlled Congress over their failure to deliver big gains on social issues even before the congressional page scandal involving former Rep. Mark Foley.
Haggard, who had been president of the evangelical association since 2003, has participated in conference calls with White House staffers and lobbied Congress last year on Supreme Court nominees.
Haggard founded New Life in the mid-1980s and held its first services in the basement of his Colorado Springs home.
Jones, who said he is gay, said he was upset when he discovered who Haggard was and found out that New Life had publicly opposed same-sex marriage - a key issue in Colorado, with a pair of issues on Tuesday's ballot.