Same-sex couples can now have their marriage blessed by the Church in Wales after a vote was held.
However, the church will still not marry same-sex couples.
Former Dean of St Albans, the Very Reverend Jeffrey John, supported the change but described it as a "halfway house" that did not go far enough.
The Evangelical Fellowship opposed the move, saying it did not uphold the "standard of Christian marriage between one man and one woman".
But Wales' bishops said it was a step on the way towards repentance of a history which has "demonised and persecuted gay and lesbian people".
Individual clergy will be able to opt out of offering blessings to same-sex couples and some conservatives said the change would cause a split.
The bill authorising a service of blessing was passed by all three orders of the church's governing body at a meeting in Newport.
The bishops passed it unanimously, the clergy passed it by 28 to 12, with two abstentions, and the laity passed it by 49 to 10, with one abstention.
The change is significant because a blessing, in theological terms, signifies God's approval.
Bishop of St Asaph, Gregory Cameron, who introduced the bill, said he felt "no sense of triumph", but added that "the Church in Wales has done the right thing under God for the LGBTQIA+ community".
Ruth Eleri James has both a personal and professional interest in the vote.
As a woman in a same-sex relationship, she said she supported giving recognition to relationships like hers as a means of showing their validity in the wider community.
She is also a trainee priest with the Church in Wales.
Although unable to vote on the proposed change because of her junior status, she said she would back the bill all the way if she were able to, as has her partner Hannah, a lay member of the governing body.
She said: "It's so important to us because it will reflect the real love and welcome that we have personally experienced in our local churches, who we know long to be able to offer something to couples who are in same-sex relationships.
"But it's also important because this is a message to LGBTQ folk in society at large to say their relationships are loved and blessed by God, and that's a message that hasn't been given, certainly in my lifetime, and I long to be able to share that with people."
Ruth said she saw the contradiction expressed by other people in the LGBT community that the church would still not offer full marriage even as it blesses legal unions formed outside of its walls.
"Hannah and I feel strongly that God is asking us to be married one day and we will continue to hope and work and pray for the day when we can have what we call the sacrament of marriage in a church," she added.
"I do see the difficulty in not being able to have that and I do see the point of people who say this doesn't go far enough. But I think a step towards justice is a step in the right direction."
However her feelings are not shared by all.
Her fellow believer, Niki Stark Devlin, said lots of the LGBT community was "very likely" to avoid the blessings, calling the offer "placatory" and "meaningless".
She added: "It also will set back actual equal marriage back by a long way as many of the heterosexual community will now feel that they've 'made a gesture' and that should be sufficient.
"I can not see many wanting a 'blessing' if they can instead move to either Quakerism [her religion] or the United Reformed Church and have an actual marriage in the eyes of God."
Blessings will now be available after an official marriage or civil partnership at a register office, but it will be up to individual clergy to decide whether or not they wish to lead it.
The bishops who proposed the bill said the church had forced gay people "into fear, dishonesty and sometimes even hypocrisy, and which has precluded them from living public and honest lives of committed partnership".
But Dr John, originally from Tonyrefail, Rhondda Cynon Taf, said there remained a big difference between the official stance of the church and the opinion of its congregation.
"Officially the church still says marriage is to be between a man and wife, but it is obvious that the views of church members have changed rapidly in recent years - especially after the government has legalised same-sex marriage," he said.
"The most important thing about the blessing service is its theological meaning. The blessing by the church defines a gay relationship as a gift from God rather than a sin."
Dr John accused the church of homophobia in 2017 when he was rejected for the position of Bishop of Llandaff - a claim it rejected.
He said he had been told appointing him would be difficult because he was in a civil partnership, although celibate, in line with Church of England teaching.
The Church in Wales does not require gay clergy to be celibate.
In 2003 he was nominated as Bishop of Reading but then asked to withdraw by the Archbishop of Canterbury.
"The Anglican Church in Scotland has already voted to go all the way - they marry gay couples without a difference," he said.
"In Wales, only a blessing will be available, so the inequality between gay couples and straight couples will remain."
In 2019, the church elected Cherry Vann, who was in a civil partnership, as Bishop of Monmouth.
The position around the UK
The Church of England does not currently recognise same-sex marriages, forbids clergy to bless same-sex unions and only allows celibate gay and lesbian clergy to minister.
The Scottish Episcopal Church voted to allow gay couples to marry in church in 2017, making it the first major Christian church in the UK to allow same-sex marriages.
According to the website of the Church of Scotland, it does not currently allow gay marriage.
The first same-sex religious wedding in Northern Ireland took place in December after changes in the law were introduced by the Northern Ireland Office.
The Reverend Josh Maynard, of Angle Peninsula Churches in Pembrokeshire, sits on the Church's governing body but was unable to attend the meeting.
Were he able to attend, he would have voted against the proposals.
"I'm quite anxious about it," he said ahead of the decision. "It is a significant vote for the Church in Wales, it will be the first major change in the teaching of the Church in Wales."
He feared it could lead to a split in the Church.
"It is a serious decision that will likely lead to fractures at best if not a complete split," he said.
He worried there will be hurt on both sides "whichever way it goes".
"What's important is that those on both sides of the debate engage with and listen to what is being said."
He said voting against the proposals did not make people homophobic.
"If you are LGBT you are welcome in any of my churches," he said.
The Evangelical Fellowship in the Church in Wales said it did not support the bill on the basis of a declaration it made in 2018.
Made at its annual general meeting that year, it said: "We acknowledge God's creation of humankind as male and female and the unchangeable standard of Christian marriage between one man and one woman as the proper place for sexual intimacy and the basis of the family.
"We repent of our failures to maintain this standard and call for a renewed commitment to lifelong fidelity in marriage and abstinence for those who are not married."
The Reverend Enid Morgan, one of the first women to be ordained as a priest in Wales, said the move would be a significant step for gay Christians.
"These are people who love each other and want God's blessing and the recognition of the church that their relationship is a valuable human relationship," she said.
"Everyone will not be happy, but people 20 years ago were unhappy to ordain women. People 20 years before that had terrible concerns about divorce."
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