Question to the Ministry of Justice:

To ask the Secretary of State for Justice, what estimate he has made of the number of prisons where drugs have been found to be manufactured in each of the last three years.

There have been no proven cases of prisoners manufacturing forensically identifiable substances in custody that would, under lab conditions, be proven to be a known drug. There is a remote chance of some prisoners experimenting with chemicals to produce substances that may/may not have a psychoactive effect, but this is unlikely to be undertaken in an organised manner or with the equipment required to produce the desired effects.