On Monday, the front page of The Sun bore the headline '1 in 5 Brit Muslims’ sympathy for jihadis', with the story beginning: "Nearly one in five British Muslims has some sympathy with those who have fled the UK to fight for IS in Syria. The number among young Muslims aged 18-34 is even higher at one in four."
However, questions were asked in other media about the survey's methodology - and the poll was mocked by Twitter users who made up comic 'facts' about other things that a fifth of Muslims did.
Survation, the polling company that conducted the research for the paper, said in a statement issued on Tuesday that it believed its poll was "broadly representative and meets acceptable methodological standards for media publication".
However, it also distanced itself from the way its data was used, saying: "There is a distinction between the work we do and how clients chose to present this work. Survation does not support or endorse the way in which this poll’s findings have been interpreted."
In a statement issued at lunchtime today, IPSO said that it had received 2,600 complaints about the article as of the morning of Thursday, 25 November, and that in line with its policy when dealing with a large volume of complaints, it had selected a lead complaint and launched an investigation.
"In this case, IPSO has selected MEND (Muslim Engagement & Development) as the lead complaint. We have written to The Sun to inform them that we have commenced an investigation into this matter," IPSO's statement said.
MEND told PRWeek it would be issuing a statement later today. The organisation describes itself on its website as "a not-for-profit company working towards enhancing the active engagement of British Muslim communities in our national life, particularly in the fields of politics and the media", and was founded by entrepreneur Sufyan Gulam Ismail.
A spokesman for The Sun said: "The Sun awaits the submission from IPSO and will respond in the usual way."
The paper has stood by its coverage in previous statements issued to other media in recent days.