Around 2.5 million households contained members from at least two different ethnic groups in 2021, the Office for National Statistics (ONS) said.
This is 10.1 per cent – an increase from 8.7 per cent in 2011, the ONS said.
It comes as 81.7 per cent of residents in England and Wales described themselves as white on the day of the 2021 census, down from 86.0 per cent a decade earlier.
Within this group, 74.4 per cent (44.4 million) identified their ethnic group as ‘English, Welsh, Scottish, Northern Irish or British’ – down from 80.5 per cent (45.1 million) in 2011, and from 87.5 per cent (45.5 million) in 2001.
The second most common ethnic group was ‘Asian, Asian British or Asian Welsh’ at 9.3 per cent – up from 7.5 per cent in 2011.
Wolverhampton was identified as the local authority with the largest percentage of people with Panjabi as a main language, at 6.5 per cent, or 17,000.
Among the three largest changes was the rise in the number of people in the UK identifying as ‘White: Other White’, which stood at 3.7 million (6.2 per cent) in 2021, up from 2.5 million (4.4 per cent) in 2011.
The largest groups in this category include ‘White: Polish’, with 614,000 (one per cent) of the overall population identifying this way, and ‘White: Romanian’, with 343,000 people (0.6 per cent) identifying this way.
People ticking the ‘Black, Black British, Black Welsh, Caribbean or African: African’ category rose to 1.5 million (2.5 per cent), up from 990,000 (1.8 per cent) in 2011.
The ONS said many factors may be contributing to the changing picture, including differing patterns of ageing, fertility, mortality, and migration.
Census deputy director Jon Wroth-Smith said. “Today’s data highlights the increasingly multi-cultural society we live in.
“The percentage of people identifying their ethnic group as ‘White: English, Welsh, Scottish, Northern Irish or British’, continues to decrease.
“Whilst this remains the most common response to the ethnic group question, the number of people identifying with another ethnic group continues to increase.”
Mr Wroth-Smith says the picture varies depending on where you live.
London remains the most ethnically diverse region of England, where just under two-thirds identify with an ethnic minority group, a figure that is only just higher than the West Midlands. Birmingham is among parts of the country where people identifying as white now form a minority of the population, at under 49 per cent.
Fewer than one in 10 identify this way in the North East, but in all areas of the UK, the vast majority of people identify themselves most as being British.
Today figures also reveal that the proportion of people in England and Wales identifying as Christian has fallen below 50 per cent for the first time.
Some 46.2 per cent of the population described themselves as Christian on the day of the 2021 census, down from 59.3 per cent a decade earlier, the Office for National Statistics said. This is the first time the proportion has dropped below half.
The Isle of Anglesey and Flintshire both had the highest proportion of people declaring themselves as Christian, at 51.5 per cent.
The percentage of people saying they had no religion jumped from around a quarter in 2011 (25.2 per cent) to over a third in 2021 (37.2 per cent).
There were increases in the proportion of people describing themselves as Muslim (up from 4.9 per cent to 6.5 per cent) and Hindu (from 1.5 per cent to 1.7 per cent).
The Archbishop of York said the country had “left behind the era when many people almost automatically identified as Christian”.
The Most Rev Stephen Cottrell said: “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.”
Humanists UK ran a campaign in the run-up to the 2011 and 2021 censuses encouraging non-religious people to tick the “no religion” box on the form.
Chief executive Andrew Copson said the figures should be a “wake-up call which prompts fresh reconsiderations of the role of religion in society”.
He said: “These results confirm that the biggest demographic change in England and Wales of the last 10 years has been the dramatic growth of the non-religious.
“They mean the UK is almost certainly one of the least religious countries on Earth.”
The National Secular Society said the figures show that aspects of society such as the Anglican establishment and daily prayers and worship in parliament and schools, are “all inappropriate, hopelessly outdated and fail to reflect the country we actually live in” and called for reform.
Chief executive Stephen Evans said: “It’s official – we are no longer a Christian country.”
He added: “The current status quo, in which the Church of England is deeply embedded in the UK constitution, is unfair and undemocratic – and looking increasingly absurd and unsustainable.”
Some 0.7 per cent of people in England and Wales (405,000) chose to write in the name of a religion that was not listed as one of the main choices. Among these, 74,000 people wrote pagan, 26,000 Alevi, 25,000 Jain and 13,000 Wicca. The largest increase was seen was in those following shamanism, up from 650 in 2011 to 8,000 in 2021.
The 2021 survey was filled out by more than 24 million households in England and Wales.