The proportion of people who said they were Christian was 46.2%, down from 59.3% in the last census in 2011, reports BBC.
In contrast the number who said they had no religion increased to 37.2% of the population, up from a quarter, the British media reported.
Interestingly, those identifying as Muslim rose from 4.9% in 2011 to 6.5% last year.
The Office for National Statistics (ONS) carries out the census in every 10 years.