The population of England and Wales has reached 56.1 million, up by 3.7 million in a decade, the 2011 Census shows.
It is the largest growth shown by any census since 1801.
The population in England was about 53 million on 27 March 2011 when the Census was taken, about 400,000 more than official estimates.
In Wales the population was 3.06 million. Around 55% of the 3.7m increase was attributed to net migration.
The public were asked questions about their jobs, health, education and ethnic background. It was the first time people could fill in the form online.
The form was compulsory, but a question about religion was optional. The answers are used to plan public services.
Three different censuses happened on the one day. Northern Ireland and Scotland each managed their own, and these were run separately from the one which was sent to 26 million households in England and Wales.
