Reports claimed MoD guidelines required interview requests from newspapers be approved by the department’s press office.
Separate reports emerged suggesting the MoD did not respond to an offer of help from the press watchdog over the handling of the captives.
The Times reported that a departmental document, entitled Defence Council Instructions General, requires that “authorisation should be obtained from the chief press officers in the D News organisation”.
The Tories said the revelation undermined Defence Secretary Des Browne’s account of how the decision was made.
Mr Browne had stressed that the actual decision had been taken by the Navy, and he was only asked to “note” the reasons behind it last Friday.
Shadow defence secretary Dr Liam Fox said: “The disclosure of these regulations, contradicting the Defence Secretary’s version of events, raises yet more questions. His authority and credibility are fast disappearing by the minute.”
The Daily Telegraph reported the MoD ignored an offer of help from the Press Complaints Commission (PCC) over the hostages.
A spokesman for the PCC said: “On Thursday April 5 we approached the MoD to offer our services through them to the hostages and their families in case problems arose with media interest.”
He said they received no response.