More than a quarter of a million pounds of public money has been spent on legal fees to attempt to block the publication of the Prince of Wales's letters to ministers, parliament has been told.
Eight Government departments have spent a total of £274,481.16 so far trying to prevent the release of Charles's letters, Attorney General Dominic Grieve said.
Ministers will seek to recover all its costs from the Guardian newspaper if it is successful in preventing publication of the letters.
Guardian journalist Rob Evans has been trying to make the letters public under the Freedom of Information Act and in September 2012 a High Court ruled in his favour.
Government departments did not intervene at the time but Grieve overruled the decision a month later.
But earlier this month, the Court of Appeal ruled that Grieve had "no good reason" for overriding the High Court's decision and said his veto was incompatible with EU law.
Grieve then claimed that releasing the letters would undermine the principle of the heir to the throne being politically neutral and was granted permission to appeal against the latest ruling to the Supreme Court.
In a written parliamentary answer to Labour's Paul Flynn, MP for Newport West, Grieve said: "The case raises issues of constitutional significance, including upholding Parliament's intentions for the Freedom of Information regime and the Government's ability to protect information in the public interest."
He went on: "Eight Government departments have had to work together on the Government's response, at a total cost of £274,481.16 (exc VAT).
"These costs encompass all costs billed by the Treasury Solicitor, including counsels' fees and disbursements.
"If we are successful in the next stage of legal proceedings the Government would seek to recover a substantial proportion of these costs from the Guardian."
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