Correspondence between Buckingham Palace and the Government over the upkeep of the Queen's palaces may be made public following a ruling under Freedom of Information laws.
The information commissioner directed the Department for Culture, Media and Sport (DCMS) to release the letters to The Independent after a long-running fight by the newspaper.
A DCMS spokesman said it had 35 days to decide whether to appeal to the Information Tribunal over the ruling, which is being studied by Government lawyers.
No details are yet known of the contents of the 100 letters and memos written by ministers and members of the Royal Household during negotiations over public subsidies for the palaces.
DCMS has so far refused to release the documents, on the grounds that it wished to respect the confidentiality of members of the Royal Household and would inhibit the free and frank exchange of views between ministers and Palace aides.
But deputy information commissioner Graham Smith said the commissioner believes "that disclosure of the requested information would enhance public awareness and understanding of the funding and accommodation arrangements of the Royal Household and this would be in the public interest".
