Downing Street has condemned the publication of leaked US diplomatic cables thought to feature embarrassing criticism of David Cameron, the Duke of York and the British military.
Washington was at the centre of an international storm after newspapers began publishing details from more than 250,000 secret embassy missives obtained by the WikiLeaks website.
The cables shed light on American dealings with governments around the world and show that Arab leaders have repeatedly urged the US to take military action against Iran.
The spotlight is set to be thrown on UK-US relations over the coming days with further disclosures expected to contain criticism of the Prime Minister and the Duke of York. UK military operations in Afghanistan are also said to be a target.
The Prime Minister's spokesman condemned the publication of the leaks by newspapers, including The Guardian, on the grounds that they could damage British and American national security. "Clearly we condemn the unauthorised release of classified information," he said. "The leaks and their publication are damaging to national security in the United States and in Britain, and elsewhere. It's important that governments are able to operate on the basis of confidentiality of information."
He added: "It has the potential to be damaging (to national security) but the very fact that this is inhibiting the conduct of governments... governments need to be able to operate on a confidential basis when dealing with this kind of information, and the very fact that it is being leaked is damaging."
The Guardian said it would be publishing details later in the week including allegations of "inappropriate behaviour" by a member of the Royal Family which was said to have "startled" US diplomats.
There was no immediate response from Buckingham Palace to a report in the Daily Mail that the member of the Royal Family involved in allegations of "inappropriate behaviour" was the Duke of York. The paper said that the Duke - who is a UK trade envoy - had shocked Americans with his "rude behaviour abroad".
The WikiLeaks documents are also said to include "serious political criticism" of Mr Cameron and "devastating criticism" of British military operations in Afghanistan.
But Guardian editor Alan Rusbridger defended his newspaper's publication of leaked information, saying: "I think it's a good thing that newspapers should bring this stuff into the public arena. It's not the job of the media to worry about the embarrassment of world leaders who have been caught saying different things in public or private, especially some of these Gulf states that don't have a free press."