Responding to the data, the Archbishop of York said the country had “left behind the era when many people almost automatically identified as Christian”.
The Most Reverend Stephen Cottrell said: “The Christian church exists to share the good news of Jesus Christ, serve our neighbour and bring hope to a troubled world. That’s what we’ve done for 2,000 years, in times of war and peace; hardship and plenty; revival and decline and it’s what we must do now more than ever.
“It’s not a great surprise that the Census shows fewer people in this country identifying as Christian than in the past, but it still throws down a challenge to us not only to trust that God will build his kingdom on Earth but also to play our part in making Christ known.
“We have left behind the era when many people almost automatically identified as Christian but other surveys consistently show how the same people still seek spiritual truth and wisdom and a set of values to live by.
“This winter – perhaps more so than for a long time – people right across the country, some in desperate need, will be turning to their local church, not only for spiritual hope but practical help. We will be there for them, in many cases, providing food and warmth. And at Christmas millions of people will still come to our services.
“At the same time, we will be looking beyond our immediate surroundings, remembering we are part of a global faith, the largest movement on Earth and its greatest hope for a peaceful, sustainable future.”
Meanwhile, the number of people in England and Wales identifying their ethnic group as white has fallen by around 500,000 over a decade.
Some 81.7% of residents in England and Wales described themselves as white on the day of the 2021 census, down from 86.0% a decade earlier, ONS said.
The second most common ethnic group was “Asian, Asian British or Asian Welsh” at 9.3%, up from 7.5% in 2011.
The ONS said large ethnicity changes were seen in people identifying as “White: Other White”, which stood at 3.7 million (6.2%) in 2021, up from 2.5 million (4.4%) in 2011.
And numbers of people identifying their ethnic group as “Other ethnic group: Any other ethnic group” rose to 924,000 (1.6%), up from 333,000 (0.6%) in 2011.
Around one in 10 households (2.5 million) contained members from at least two different ethnic groups in 2021.
This is an increase from 8.7% in 2011, the ONS said.