Finland's largest religious body will not allow its pastors to officiate same-sex weddings, despite country-wide legislation that will allow gay couples to marry next year.

The Evangelical Lutheran Church of Finland, which has around four million members, has issued guidelines to church leaders that says the new law on March 1, 2017, will "have no effect on the rights of pastors to officiate church weddings".

The Bishops' Conference, which wrote the guidelines, said that the Church Handbook states that marriage is between a man and a woman, and this will not change.

However, the Helsinki Times reports, church leaders may pray with and for couples who enter into civil marriages.

The bishops also insisted that "same-sex couples are welcome to take part in all church activities".

"Church members will include married same-sex couples after 1 March, 2017. As has been noted previously, the church is for everyone," the bishops said.

"Same-sex couples are welcome to all church activities and shall be treated as families, even though they have not entered into marriage in accordance with the Church Act."

The Evangelical Lutheran Church is one of two national Churches in Finland. The other is the Finnish Orthodox Church.

The Church of England has for decades been grappling with same-sex marriage, and the issue has been highlighted once again after one of its bishops became the first to come out as gay on Friday.

The Bishop of Grantham, Nicholas Chamberlain, made the announcement in an interview with the Guardian. He said that his sexuality was known by his senior bishop and the Archbishop of Canterbury when he was appointed last November.

Church of England guidelines for bishops stipulate that gay clergy must be celibate.

Archbishop Justin Welby said Chamberlain's sexuality is "completely irrelevant to his office".