Official statistics
"Official statistics are statistics produced by crown bodies, those acting on behalf of crown bodies, or those bodies specified in statutory orders" (Office for Statistics Regulation, Code of Practice for Statistics, Glossary - 2021)
This describes numerical data collected by government departments, or on behalf of government, and that is published for statistical purposes.
The UK Statistics Authority defines types of official statistics and these include national statistics and official statistics in development (formerly known as 'experimental statistics').
The Code of Practice for Statistics (Office for Statistics Regulation) sets the standards that producers of official statistics should comply with.
Unofficial statistics
This describes numerical data collected by independent organisations.