The Campaign for Freedom of Information said some departments only release responses to FOI requests after approval by ministers’ special advisers (Spads) at Stormont.

Maurice Frankel, director of Campaign for Freedom of Information, said: “They run the risk of overstepping the line and being seen to be withholding information which ought to be disclosed.

“They may be taking a risk by putting it through an explicitly political process, and the question is how are they using this process.”

He added: “It shouldn’t be necessary for ministers or special advisers to be examining responses before they are going out.”

The Information Commissioner’s Office (ICO) said: “Freedom of Information law doesn’t specify a sign-off process for FOI requests. It is up to individual organisations how they deal the internal process.”

A spokesperson for the Department of Justice defended its own process: “Responses are only forwarded to the ministerial/press office or Spad for their approval where it is felt they would be affected in some way by the public release of the information requested.”

All requests refused on the basis of “prejudice to the effective conduct of public affairs” are approved by Justice Minister Claire Sugden.