Mormon Church founder Joseph Smith had as many as 40 wives, some already married, the church leaders admitted for the first time.

Joseph Smith was portrayed in Mormon Church materials as a loyal partner to his loving spouse Emma Hale.

The church’s disclosures, in a series of essays online, are part of an effort to be transparent about its history at a time when church members are increasingly encountering disturbing claims about the faith on the internet.

Many Mormons, especially those with polygamous ancestors, say they were well aware that Joseph Smith’s successor, Brigham Young, practiced polygamy when he led the flock in Salt Lake City. But they did not know the full truth about Joseph Smith.

Joseph Smith probably did not have relations with all of his wives, because some were “sealed” to him only for the next life, according to the essays posted by the church. But for his first wife, Emma, polygamy was “an excruciating ordeal”.

Joseph Smith was portrayed in Mormon Church materials as a loyal partner to his loving spouse Emma Hale

The four treatises on polygamy reflect a new resolve by a church long accused of secrecy to respond with openness to the kind of thorny historical and theological issues that are causing some to become disillusioned or even to abandon the faith.

The Church of Jesus Christ of Latter-day Saints, as the Mormon Church is formally known, has quietly posted 12 essays on its website over the last year on contentious topics such as the ban on blacks in the priesthood, which was lifted in 1978, and accounts of how Joseph Smith translated the Book of Mormon, the church’s sacred scripture.

Elder Steven E. Snow, the church historian and a member of its senior leadership, said in an interview: “There is so much out there on the Internet that we felt we owed our members a safe place where they could go to get reliable, faith-promoting information that was true about some of these more difficult aspects of our history.

“We need to be truthful, and we need to understand our history.

“I believe our history is full of stories of faith and devotion and sacrifice, but these people weren’t perfect.”

The essay on “plural marriage” in the early days of the Mormon movement in Ohio and Illinois says polygamy was commanded by God, revealed to JosephSmith and accepted by him and his followers only very reluctantly. Abraham and other Old Testament patriarchs had multiple wives, and Joseph Smith preached that his church was the “restoration” of the early, true Christian church.

Most of Joseph Smith’s wives were between the ages of 20 and 40, the essay says, but he married Helen Mar Kimball, a daughter of two close friends, “several months before her 15th birthday”. A footnote says that according to “careful estimates,” Joseph Smith had 30 to 40 wives.

In 1890, under pressure by the American government, the church issued a manifesto formally ending polygamy. The church’s essay on this phase admits that some members and even leaders did not abandon the practice for years.

However, the church did renounce polygamy, and Mormons who refused to do the same eventually broke away and formed splinter churches, some that still exist. Warren Jeffs, the leader of one such group, was convicted in Texas in 2011 of child assault.

There remains one way in which polygamy is still a part of Mormon belief: The church teaches that a man who was “sealed” in marriage to his wife in a temple ritual, then loses his wife to death or divorce, can be sealed to a second wife and would be married to both wives in the afterlife. However, women who have been divorced or widowed cannot be sealed to more than one man.