This paper states that the UK recognises the importance of continuing to respect obligations of confidentiality and to protect information exchanged while it was a Member State, and that arrangements agreed with respect to confidentiality and the handling of information produced while it was a Member State should be reciprocal, affording an equivalent level of protection to the UK and the EU after the UK’s withdrawal.
These protections should be equivalent to those set out in the existing regimes.
Read the position paper here: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/638957/Confidentiality_and_access_to_documents_Position_Paper.pdf or via the PDF attached below.