Three High Court judges have refused to overturn a decision blocking the disclosure of correspondence written by the Prince of Wales to Government ministers, as they believe it could undermine his ability to fulfil his duties as King.
Publication of the letters was blocked by Attorney General Dominic Grieve in October 2012 and this decision was upheld by the Lord Chief Justice, Lord Judge, Lord Justice Davis and Mr Justice Globe on Tuesday.
They ruled that blocking the release of the letters was lawful and that Mr Grieve had reasonable grounds for deciding it was “an exceptional case meriting use of the ministerial veto to prevent disclosure and to safeguard the public interest”.
Mr Grieve, the Government's principal legal adviser, said his decision was based on his view that the correspondence was undertaken as part of the Prince's “preparation for becoming king”.
Making the letters public could potentially damage the principle of the heir to the throne remaining politically neutral, and so would undermine his ability to fulfil his duties when king, he argued.
The Government had been ordered to disclose letters sent by Prince Charles to Government ministers during a seven-month period between 2004 and 2005 after Guardian journalist Rob Evans won a freedom of information appeal.
Prince Charles had written to seven departments: Business, Innovation and Skills, Health, Children, Schools and Families, Environment, Food and Rural Affairs, Culture, Media and Sport, the Northern Ireland Office and the Cabinet Office.
Three judges at a freedom of information tribunal allowed Mr Evans's challenge against the Information Commissioner, who had upheld refusals by the Government departments to release the correspondence.
The tribunal judges ruled that Mr Evans was entitled to “advocacy correspondence” written by Charles, described as letters he had written seeking to advance the work of charities or to promote views.
But Mr Grieve issued a certificate vetoing disclosure under section 53 of the Freedom of Information Act 2000 and under the Environmental Information Regulations 2004.
Dinah Rose QC, appearing for Mr Evans, argued at the High Court the use of the veto was legally flawed and the Attorney General had “adopted an impermissible blanket approach, unreasonably failing to consider the public interest balance in respect of each individual piece of correspondence”.
But Lord Justice Davis said the reasons given by Mr Grieve were “proper, rational and make sense” and he was entitled to consider the prince's correspondence as a whole.
Ms Rose's argument that section 53 could not lawfully be used in respect of environmental information was rejected because “the exercise by the executive of that power to override the decision of an independent and impartial tribunal” was incompatible with EU law.
The judge, with whom both other judges agreed, said: “Since, as I have concluded, the Attorney General had reasonable grounds for certifying as he did, the challenge in so far as it relates to requests for disclosure of environmental information also fails.”
Campaign for Freedom of Information director Maurice Frankel said: "The Lord Chief Justice has highlighted the scale and power of the ministerial veto which it says could even be used to overturn a decision of the Supreme Court - a situation which he says is unprecedented in domestic law.
"The only, very limited safeguard, is judicial review.
"But as this case shows, the veto will be upheld at judicial review even if the disclosure decision is thoroughly and well argued and contains no error.
"Ministers don't have to show they are right and the tribunal or court is wrong, only that they have reasonable grounds for taking a different view about the public interest.
"The veto is a powerful tool and judicial review too limited a safeguard.
"Ministers should have to appeal against decisions they dislike and not be able simply to overturn them."
Additional reporting by PA