Finland's Evangelical Lutheran Church has been hit by a wave of resignations in connection to its Archbishop's open support for same-sex marriage, according to the YLE news service.

The country's parliament voted on Friday to allow same-sex marriages, a move welcomed by Archbishop Kari Mäkinen. However, the Archbishop's statement triggered a wave of defections from the Church, with nearly 12,000 registered on the "Leave the Church" website during last weekend alone. The true number leaving may end up considerably less as the process for leaving the Church requires a letter to the local register office, but it is an indication of the strength of feeling regarding the Archbishop's comments.

Finland's Lutheran Church is the country's established religion and around 75 per cent of Finns are members, paying a special church tax. The surge in resignations during the weekend has clearly been driven in part by the Archbishop's remarks, but resignations have in any case increased in recent years thanks partly to the efforts of agnostic campaigners – who set up the "Leave the Church" website to make it easier for members to leave – partly because more Finns wish to avoid paying the Church tax, and partly because the general opposition of the Church to same-sex relationships has not played well in a largely liberal and secular society.

According to the head of the agnostics association, Petri Karisma, while most of those who chose to leave the church appeared to be conservatives angered by Archbishop Mäkinen's support for gender-neutral marriage, liberals objected to the Church's overall position. "In spite of Archbishop Kari Mäkinen's positive comments the church's official position on same-sex marriage is negative. This has now led to a situation where liberals are also leaving," Karisma told the Iltalehti daily paper.

He also said that during the last peak of resignations the website recorded 9,000 resignations following disparaging statements about gay marriage by Christian Democrat interior minister Päivi Räsänen in 2010. She has said she will continue to fight against the legislation.

In an attempt at damage control, two bishops – Rt Revs Seppo Häkkinen and Björn Vikström – issued a joint letter saying that they disagreed on the question of gay marriage, but urging unity. "However, we are completely agreed that no one should resign from the church over this matter," the statement said.

Vikström said that the Church was the focus of protests at the parliament's decision. "People are disappointed and want to protest. As they cannot resign from the state or from the parliament, then at least some of that anger has been focused on the church and on the archbishop's comments," he said.

The Bishop of Espoo, Tapio Luoma, said that the parliament's decision was not a signal that same-sex marriages could now take place in churches. "It's clear that the church will make its own decisions according to its own beliefs," he said. "On the other hand developments in wider society have affected decision-making before. The Church cannot close itself off."

Archbishop Mäkinen's support for same-sex relationships has had ecumenical consequences recently, with members of the Russian Orthodox Church cancelling a joint summit meeting with Finnish Lutherans over his stance.

Archbishop Mäkinen said that the Russians demanded that he sign a statement condemning gays and lesbians in advance of the planned event and that he had refused.