The number of people in Britain identifying as Christian is in "dramatic decline", according to the latest figures from the British Social Attitudes Survey.
The proportion identifying as Christian stands at 38%, down from half in 2008 and nearly two-thirds in 1983. It is the first time that the figure has fallen below 40%.
At the same time, there has been a continued rise in the percentage of Brits identifying as Muslim, from 1% in 1983 to 3% in 2008 and 6% in 2018.
There has also been a substantial increase in those who do not identify with any religion, up from 31% in 1983 to over half of those polled in 2018 (52%).
The survey of 3,879 people revealed that people were more likely to "feel positive" towards Christians (51%) than towards Muslims (30%).
Only 4% said they had negative perceptions of Christians, compared with 17% for Muslims.
But nearly two thirds of those surveyed (63%) agreed that religions brought more conflict than peace.
Christians who said they did not belong to any denomination have also increased since 1983, from just 3% to 13% last year.
Those who said they never pray was also up from 41% in 2008 to 50% in 2008.
The report by the National Centre for Social Research said the findings were "compelling evidence that the process of secularisation continues unabated".
"The past two decades have seen international conflict involving religion and domestic religious organisations, putting themselves at odds with mainstream value," it said.
"We find a dramatic decline in identification with Christian denominations, particularly the Church of England, a substantial increase in atheism and in self-description as 'very' or 'extremely' non-religious ... but tolerance of religious difference."
It added: "Britain is becoming more secular, not because adults are losing their religion but because older people with an attachment to the Church of England and other Christian denominations are gradually being replaced in the population by unaffiliated younger people.
"To put it another way, religious decline in Britain is generational - people tend to be less religious than their parents, and on average their children are even less religious that they are."