An article in The Sun headlined "1 in 5 Brit Muslims' sympathy for jihadis" has been found to be misleading by the Independent Press Standards Organisation (Ipso).
The press regulator ruled the article breached Clause 1 of the Editor's Code, which relates to accuracy.
The story, published on 23 November, reported the results of a survey of British Muslims, but generated more than 3,000 complaints.
The article said "nearly one in five British Muslims has some sympathy with those who had fled the UK to fight for IS in Syria", but also noted that the survey showed "a clear majority of the 2.7 million Brits who follow Islam are moderate".
The story was illustrated on the front page with a photograph of Mohammed Emwazi, a militant with the so-called Islamic State, captioned "Support ... Brit Jihadi John who went to Syria".
The question about sympathy asked respondents about those "who leave the UK to join fighters in Syria".
Complainants argued that, as the question did not mention so-called Islamic State, those who responded to the question might not have intended for their answers to be understood as relating to those joining the group; a number of British Muslims had left the UK to fight against Islamic State, or alongside anti-Assad forces or various Sunni groups.
The Sun did not accept that the meaning of "those who leave the UK to join fighters in Syria" was ambiguous.
It said that previous questions in the telephone survey had made explicit reference to Islamic State and the overwhelming majority of those who leave the UK to join fighters in Syria are joining the group.
As the regulator received so many complaints, it chose Muslim Engagement & Development as the lead complainant and upheld the complaint after considering the coverage.
Ipso also upheld a complaint about the headline of an article in The Times which reported the Sun's survey under the headline "One in five British Muslims has sympathy for Isis".
The Sun published the adjudication on page two of the paper on Saturday, as required by Ipso.