Two centuries of official standing and almost a millennium of traditional connection may be unravelled if a Finnish secularist group successfully gather 50,000 signatures in the next six months.
The Finnish Citizen's Initiative website began collecting "statements of support" on Monday for a plan to introduce legislation that will abolish the privileged position of the state Churches.
Under constitutional rules, if 50,000 signatures from Finnish voters are gathered within six months, legislation on the matter must be discussed in Parliament.
If passed, this law would mean the Evangelical Lutheran Church of Finland and the Orthodox Church of Finland would lose their status as public corporations, ending their inclusion in public administration.
In the Helsinki Times, the chair of the Union of Freethinkers of Finland, Petri Karisma said: "I'm not expecting the Parliament to rush into revising the laws, but we must be able to have an objective debate about this.
"The constitution stipulates that people should not be discriminated based on their religious convictions. People also have the right to religion and conscience. Other legislation fails to comply with these principles."
In a country of 5.26 million, Mr Karisma asked: "With the number of irreligious citizens already breaching the one-million mark, is the position of the state church still justified?"
The Churches are currently able to levy taxes on the population which are collected through the state, and public holidays laid out in a law known as "the Church Act" cannot be altered without permission from the state church's General Synod.
Official marriage licences can only be granted by the state Churches, or religious groups registered with the state. Non-religious groups and unregistered religions are not catered for in this system.
One of the points of contention for the secularists is that in Finnish schools, while there are options to have classes on either religion or ethics, the classes children take are determined by their religious beliefs rather than individual choice.
"If asked, you don't have to reveal what party you voted for. But at schools, everyone must reveal their religious convictions, and religious teaching is determined on that basis," Karisma said.
The secularists' petition highlights the European Court of Human Rights' interpretation of the freedom of religion, which includes the right not to disclose religious conviction or lack thereof.
It also demands the termination of all religious activities at nurseries, schools, and universities, as well as in Parliament, and the armed forces.
This would be the latest in a string of difficult issues for the Church in Finland to deal with.
Membership of the state Churches has been in rapid decline ever since 2003 when a website called "the equality of convictions" made it easy to de-register membership, thus cutting an individual's taxes slightly.
While in 2009 some 40,000 left the Church, in 2010 that number jumped to 70,000 after a televised discussion of whether or not homosexuality was sinful prompted widespread public outrage.
Footage of conservative activists questioning a gay couple's ability to raise a family "unleashed these repressed feelings" of hostility towards the Church, said Mr Karisma in Monocle Magazine, where he also described the Churches' attitude toward homosexuality as "a stone in the shoe for many people".
Consequently, Church finances are dwindling rapidly. With over 400,000 people leaving the Church between 2003 and 2013, it lost 464 million euros in revenue. If the current trend continues, by 2020 that figure could be 1.5 billion euros.
The advocates of this new initiative argue that all religions should be treated equally, with religion being defined as an exclusively private matter.
To have legislation sent to Parliament, the initiative needs to maintain an average of approximately 278 statements of support per day.