You asked
I would like to know how many British born Muslims are currently living in the UK according to the most recent statistics for 2019.
We said
Thank you for your request for information on how many British born Muslims are currently living in the UK. We do not hold data relating to the number of UK-born people, by religion, for the whole of the United Kingdom. We do not hold data on religion for people living in Northern Ireland because the data collected does not include a specific breakdown of Muslims.
Data relating to England, Scotland and Wales can be obtained from the ONS Social Survey Operations Division who provide an ad hoc analysis service, including tabulations of Labour Force Survey (LFS) and Annual Population Survey (APS) data which contain question variables relating to religion. This service is subject to legal frameworks, disclosure control, resources and agreements of costs, where appropriate. Details of the variables included in these datasets can be viewed in the LFS User Guides https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/methodologies/labourforcesurveyuserguidance. If you would like to enquire about this service, then please contact socialsurveys@ons.gov.uk.
If you are able to do your own cross-tabulations, you could purchase an anonymised LFS or APS dataset from the UK Data Service. Details on costs and how to download the data can be found on their website:
Advice for commercial users - http://ukdataservice.ac.uk/get-data/how-to-access/registration.aspx#/tab-commercial-users
Charges - http://ukdataservice.ac.uk/get-data/how-to-access/charges.aspx
As the information you have requested is available through this route, section 21 (1) of the Freedom of Information Act S21(1) applies and the information does not have to be supplied under the Freedom of Information Act. S21(1) is an absolute exemption and no consideration of the public interest needs to be applied.