The Methodist church will decide this week whether to take a significant step towards allowing same-sex marriage, a move likely to complicate plans for closer ties with the Church of England.

The Methodist conference in Birmingham is being urged to support proposals to allow same-sex marriage in its chapels. If successful, a final decision would be taken next year after wider consultation.

Among the Christian denominations in the UK that allow same-sex marriages are the Quakers, the Scottish Episcopal church, the United Reformed church and the General Assembly of Unitarian and Free Christian Churches. The Church of England has restated traditional doctrine that marriage is a union between a man and a woman.

The Methodist church – Britain’s fourth largest Christian denomination after the C of E, the Roman Catholic church and the Church of Scotland – set up a task group in 2016 to consider its definition of marriage in the light of legal and social changes. A report from the group to be presented to the conference this week highlights “the hurt felt by those who perceive that the current definition implies they are ‘lesser persons’ ”. At the same time, it says, feelings of “alienation and distress” among those adhering to a traditional definition of marriage should be acknowledged.

It concludes that the church should “value all committed faithful loving relationships” and offer dignity and inclusion “to those who cohabit, are single, or are developing relationships, irrespective of sexuality and gender”.

It proposes “we take steps to enable same-sex couples to get married in the Methodist church”. A clause would exempt ministers who felt prevented by their “personal beliefs and integrity” from officiating at same-sex weddings.

Methodist evangelicals opposed to the move called on Christians around the world to join a day of prayer and fasting last week aimed at upholding “the biblical understanding of marriage as the lifelong union of one man and one woman”.

Two years ago, the Scottish Episcopal church voted overwhelmingly to allow same-sex couples to marry in church. It was later sanctioned by the global Anglican communion over its decision.

C of E leaders have striven to reconcile those who want it to be more inclusive to LGBT Christians and allow same-sex marriage, and those who want to uphold traditional biblical teaching. It has set up a string of working groups to examine the issues.

The vote at the Methodist conference comes just days before the Church of England’s governing body, the general synod, is to debate controversial steps towards closer ties between the two denominations.

A proposal to allow “interchangeability” of ministers is seen by some as a move towards reunification of the two churches, which split in the 18th century.

The synod is being asked to pass an “enabling measure” to allow legislation to be drawn up. However, opposition on theological grounds is likely to be voiced, and some members of the synod will resist closer ties with a church likely to allow same-sex marriage.

• This article was amended on 2 July 2019 to clarify that more than three Christian denominations in the UK allow same-sex marriages.