The Ministry of Justice routinely publishes the number of unconvicted children on remand, which can be found here: https://www.gov.uk/government/statistics/criminal-justice-system-statistics-quarterly-december-2018. Figures for 2019 will be published later in May.
The Ministry of Justice does not centrally hold data on the reasons why children are held on remand or why they were refused bail.
The decision to grant or refuse bail is a matter for our independent judiciary. There is a general presumption to bail in criminal proceedings, but there are exceptions to this. The remand framework ensures the court considers all options, including bail and community remand options, before a remand into custody would be considered.
We are currently undertaking work to consider the use of youth custodial remand and in due course we aim to identify options to reduce the numbers of children remanded to custody where appropriate, while ensuring victims and the public are protected.