The 2011 census found 37% of people in Scotland regard themselves as non-religious.
This compared with just under one-third of the population (32%) who classed their religion as Church of Scotland and 16% who followed the Roman Catholic Church in Scotland.
A total of 1.7 million people said they were part of the Kirk family in 2011, down from more than 2.1 million a decade earlier. Some 841,000 classed themselves as Catholic, up slightly from 804,000 in 2001.
At the same time, the number of people saying they had no religion rose from 1.4 million to 1.9 million.
The two main churches said yesterday the services they provide reach a far wider number of people in Scotland and pointed out that more than half of the country (54%) still think of themselves as Christian, including other denominations.
Reverend Colin Sinclair, who is convener of the mission and discipleship council at the Kirk, said the church was still a "vibrant and important force in society".
He said the fact 1.7 million people stated their religion as Church of Scotland when the Kirk's membership was one-quarter of that level, at 400,000, reflected its wider reach.
He said: "We recognise that numbers have declined and that the census figures reflect the true number of people who identify both with the Church of Scotland, with the Christian religion in all its facets and with organised religion of all faiths. In many other ways the Church is there for everyone and seeks to serve people at their times of greatest need.
"There are many people who believe in the importance of Christian faith and worship and who want to share its message with the whole of Scotland. Over half the people of Scotland still identify with the Christian faith."
A spokesman for the Catholic Church in Scotland said: "For the number of Catholics in Scotland to show a slight increase against a backdrop of falling religious observance and identity is heartening as is the fact that over half the population still describe themselves as Christians."
Rev Sinclair said there was "still a place for strong Christian values in society".
He added: "They underpin our system of morals, ethics and justice. This and every other weekend, more people will attend church in Scotland than attend football matches. The Kirk is still that deeply enshrined in our national identity. The Church serves and supports the whole of Scotland, including the very remotest areas, in many ways."
Slightly more than 1%, or 77,000 people, reported that they were Muslim, up 34,000 in 10 years, The numbers of Buddhists, Hindus and Sikhs accounted for 0.7% of the population in 2011 in total and both have gone up since 2001. The number of Jewish people has declined slightly, to just under 6000.
Keith Porteous Wood, executive director of the National Secular Society, said: "For such a significant change to take place in such a short period indicates many who had previously described themselves as Church of Scotland now self-identify as non-religious.
"These figures should serve as a long-overdue wake-up call for school authorities to abandon religious observance in schools and to put an end to confessional and proselytising religious teaching, which is currently rife."