In the European parliament on Thursday, Michael Cashman, the MEP for the West Midlands, will argue that all documents held by the European council of ministers, commission and parliament must be made publicly accessible to EU citizens.

The draft resolution from the parliament's Citizens' Freedoms and Rights, Justice and Home Affairs committee acknowledges that although exceptions may sometimes have to be made to public access it limits those to a small number, including defence and military matters.

The move is controversial at a time when discussions are taking place about an EU-wide defence force and could jeopardise closer union links with Nato. The new regulation would see the repeal of existing rules relating to military and defence documents. And national governments with a secretive regime, like the UK's, may find that the secrecy of Nato and other defence documents submitted to the commission or the council of ministers can be challenged by appeals to the European ombudsmen or in the European Court of Justice.

Geoffrey Van Orden, Conservative MEP and spokesman on foreign affairs and defence, said: "While the overall quest for greater transparency in our public institutions is to be welcomed, particular care must be taken in the areas of security and defence... it would not be safe for NATO to send information to EU institutions, because its confidentiality could be questioned and it could end up in the public domain."

UK ministers should note that although the regulation will not amend existing national legislation governing freedom of information the commission warns that "member states should take care not to hamper [its] proper application".