The Sun's "Queen backs Brexit" headline was inaccurate, the Independent Press Standards Organisation (IPSO) has ruled.
Buckingham Palace complained about the story published on March 8 which detailed an occasion when the Queen allegedly vented her anger with Brussels at the strongly pro-EU Nick Clegg during a lunch at Windsor Castle when he was deputy prime minister.
The verdict of the Ipso ruling that found the newspaper's headline had breached Clause 1 (accuracy) of the Editors' Code of Practice was printed in an article on page two of Wednesday's edition of the newspaper.
The front-page headline read: "Queen backs Brexit" and the paper quoted a ''senior source'' as saying that people who heard their conversation ''were left in no doubt at all about the Queen's views on European integration''.
The article said two unnamed sources had claimed that the Queen made critical comments about the EU at two private functions - first with Nick Clegg at a lunch for Privy Counsellors at Windsor Castle in 2011, and at a reception for MPs at Buckingham Palace.
At the time, former Liberal Democrat leader Mr Clegg dismissed the report as ''nonsense'', while the Palace said: "The Queen remains politically neutral, as she has for 63 years.
''We will not comment on spurious, anonymously sourced claims. The referendum is a matter for the British people to decide.''
Justice Secretary Michael Gove refused to rule out being the source of the leak and The Sun said it stood by its story and planned to defend against the complaint "vigorously".
Ipso said that while the article itself did not breach the code, the headline did as it was "a factual assertion that the Queen had expressed a position in the referendum debate, and there was nothing in the headline, or the manner in which it was presented on the newspaper's front page, to suggest that this was conjecture, hyperbole, or was not to be read literally".
The article which details the ruling - ordered by Ipso as a remedy for the inaccuracy - said: "Ipso acknowledged the importance of headlines in tabloid newspapers.
"However, it did not follow from the comments the article reported that the Queen wanted the UK to leave the EU as a result of the referendum: that suggestion was conjecture and the committee noted that none of those quoted in the story were reported as making such a claim.
"The headline was not supported by the text. It was significantly misleading - given that it suggested a fundamental breach of the Queen's constitutional obligations."