Here you can read the report MEPs Access to Penitentiary Centres and Inmates in the European Union: country-by-country report and key indicators that the EU-Catalonia Dialogue Platform have elaborated, after the events of December 2017 when seven MEPs of the Platform were denied to access the prison in Estremera (Spain).
The report basically concludes that there is a discrimination between MEPs and national legislators when it comes to the access to prisons across the EU. To solve this, the EP resolution on “Prison systems and conditions” approved in November 2017 already called “on Member States to allow MEPs the right of access to prisons and detention centres without hindrance”
Download the report: MEP access to penitentiary centres and inmates_final