Up to 63,000 secret files exposed to asbestos have been put out of range of the Freedom of Information Act until they can be decontaminated.
The Belgrano was sunk during the Falklands conflict
An MoD spokesman said the files had now been removed from the old War Office building in Whitehall to a warehouse.
They are reported to contain the official account of the sinking of the Belgrano among other secrets.
The MoD said procedures were being looked at to decontaminate the files so information could be made available.
Once cleaned up, priority would be given to requests made under the Freedom of Information act which comes into effect on 1 January 2005, the spokesman said.
But in the meantime the priority had to be the health and safety of staff and the documents had been sealed in plastic bags and packed into crates.
Cold War expert Professor Matthew Jones told the Daily Telegraph: "I find it disturbing that the MoD may be able to use the excuse of asbestos not to fulfil the requirements of the act.
"These files are irreplaceable records of this nation's defence and foreign policy during the 20th Century."
The MoD spokesman would not speculate on the actual contents of files but confirmed they are thought to contain information from the 1980s.
That could include the official version of the sinking of the Belgrano in the 1982 Falklands conflict.
There will also be interest in whether files could unravel any more details of the shooting of IRA terrorists by the SAS in Gibraltar in 1988.