The Conservatives are continuing to press the government over the 15 sailors and marines who were held hostage by the Iranians.
Arthur Batchelor sold his story to the Daily Mirror
Shadow defence secretary Liam Fox is calling for an inquiry into the circumstances of their capture.
He also wants to know whether ministers decided the released hostages should be allowed to sell their stories
Dr Fox said Defence Secretary Des Browne should give "details of who was involved in the decision" and when.
A Ministry of Defence review of the rules governing the issue is under way.
Mr Browne, who was made aware that the Navy intended to allow accounts of the 13-day ordeal to be sold, imposed a ban on further sales on Monday after the publication and broadcast of the first stories sparked a backlash.
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.
Dr Fox said more detail needed to be given about the process which allowed the stories to be sold to the media in the first place.
"This is complete ministerial incompetence. Ministers utterly failed to think out the consequences of what they were doing," he said.
"Typically, New Labour's obsession with news management trumped issues of dignity, professionalism and discipline.
"The MoD's actions were completely at odds with normal procedure and totally out of character with the ethos of our armed forces."
On Tuesday, a Downing Street spokeswoman refused to be drawn on when the prime minister became aware of the decision.
She said: "This was a decision taken by the navy... I don't think it's helpful to get into who informed who when. The prime minister supports the defence secretary in the decision taken to look at this."
In the Trevor Macdonald programme, Leading Seaman Turney defended her decision to sell her story and said a percentage of the money would help the crew and families of HMS Cornwall.
"I want everyone out there to know my story from my side, see what I went through," she told the programme.
The Royal Navy crew were on patrol boats in the Gulf on 23 March when they were detained by Iran's Revolutionary Guard.
The Iranians accused the crew of straying into its waters - the British say they were in Iraqi territory.