The Press Complaints Commission (PCC) says it offered to help the Ministry of Defence deal with media interest in the 15 service personnel held by Iran.
Two of the sailors have sold their stories to the media
But the watchdog said despite the offer they heard nothing back from the MoD, it has been reported.
The Conservatives are claiming it raises questions about the way the defence secretary, Des Browne, handled the affair.
The MoD said it was "grateful as ever" for the PCC's input over the issue.
It is also understood MoD guidelines require interview requests from newspapers to be approved by the department's press office.
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."
But the PCC did not receive a response, the Daily Telegraph reported.
Downing Street has flatly denied any role in the decision to allow the navy crew freed by Iran to sell their stories to media.
Conservative leader David Cameron has also called for Tony Blair to clarify what he knew about the sale.
Mr Browne has taken responsibility for the navy's decision. He said he had not been "content" with it but believed he had no choice under the rules.
According to the Times, 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 this contrasted with the defence secretary's account of how the decision came to be made.
The decision to allow the personnel to sell their stories has drawn criticism from opposition MPs, former military figures and the families of servicemen killed or injured in Iraq and Afghanistan among others.
Only two of the 15 captured navy personnel sold their stories.
Arthur Batchelor, 20, the youngest of the British sailors to be held captive, told the Daily Mirror about his "nightmare" at the hands of his captors.
And Leading Seaman Faye Turney sold her story to ITV1's Tonight with Trevor Macdonald and the Sun newspaper - reportedly for a six-figure sum, some of which will go to navy families.
The Royal Navy crew of sailors and marines were on patrol boats in the Gulf on 23 March when they were detained by Iran's Revolutionary Guard - the Iranians said they had strayed into its waters, which the British deny.