LONDON (Reuters) - Britain's Supreme Court ruled on Thursday that 27 letters written by Prince Charles to ministers from 2004 to 2005 can be disclosed to the media, a step that could cast doubt over the political neutrality of the future king.

The Guardian newspaper had been trying since 2005 to obtain the letters from government departments using Britain's freedom of information law, but despite a court victory the Attorney-General vetoed disclosure in 2012.

After the Court of Appeal ruled last year that the ministerial veto was unlawful, the Attorney-General appealed to the Supreme Court in a last-ditch attempt to stop disclosure, arguing it could undermine Prince Charles' position. "We dismiss the Attorney-General's appeal," the court's President David Neuberger said.

The Supreme Court does not have the letters and they will not be immediately released. Government departments are in possession of the letters and it was not immediately clear how disclosure would be handled following the Supreme Court ruling.