An article in the Sun that claimed nearly one in five UK Muslims had "sympathy for Jihadis" was misleading, the new press regulator has ruled.
The paper's story in November reported the results of a survey of UK Muslims, generating more than 3,000 complaints.
The Independent Press Standards Organisation ruled it breached the accuracy clause of its editors' code.
It said the paper's presentation of the poll had been "significantly misleading".
The paper has published the regulator's ruling, as required.
The Sun's article on 23 November, based on a poll carried out after the Paris terror attacks, said "nearly one in five British Muslims has some sympathy with those who had fled the UK to fight for IS [so-called Islamic State] in Syria".
The article was illustrated on the front page with a photograph of Mohammed Emwazi - the British militant known as "Jihadi John", who was killed in a drone strike - and was captioned "Support ... Brit Jihadi John who went to Syria".
Ipso said the coverage presented as a "fact" that the poll showed one in five British Muslims had sympathy for those who left to join IS or even the group itself - although the questions and answers in the survey about "sympathy" never mentioned the IS group.
The Sun had argued the meaning of "those who leave the UK to join fighters in Syria" was not ambiguous.
The paper said previous questions in the telephone survey had made explicit reference to IS and the overwhelming majority of those who leave the UK to join fighters in Syria are joining IS.
It also noted in its story that the survey showed "a clear majority of the 2.7m Brits who follow Islam are moderate".
But in its adjudication, published on page 2 of The Sun on Saturday, IPSO concluded the newspaper had "failed to take appropriate care in its presentation of the poll results, and as a result the coverage was significantly misleading".
An Ipso spokesman said: "The newspaper had provided various interpretations of the poll result which conflated important distinctions between those travelling to Syria and those already fighting in Syria; between "sympathy" for these individuals and "support" for their actions; and between individuals attracted by the ideology of IS, and the ideology of IS itself."
Ipso also upheld a complaint about the headline of an article in The Times which reported the Sun's survey with the headline "One in five British Muslims has sympathy for Isis".
The press regulator was established on 8 September in 2014 after the Press Complaints Commission was wound up.
It rules on whether newspapers and magazines have breached its editors' code and can ask publications to print prominent corrections or critical adjudications when they are judged to have breached its code.