Ipso, the press watchdog, received a record number of complaints about the splash, in which the paper claimed its paper showed the scale of "sympathy for Jihadis" among Muslims.
The Sun's front page
But people quickly pointed out that the question in the poll only asked if they sympathised with those who travel to "join fighters in Syria," not specifying IS, also known as Isis or Isil.
The question could refer to more moderate rebel groups, such as the Free Syrian Army.
The front page has so far triggered 1,200 complaints to Ipso, the most it has ever received since it began operating in September 2014.
It is three time as many as Hopkins' April 17 column, in which she likened migrants to "cockroaches" and said their boats should be repelled by gunships. It attracted 400 complaints.
The column saw Hopkins interviewed by police on suspicion of inciting racial hatred though she was not ultimately charged.
An Ipso spokesman said it had processed 450 complaints as of 4pm on Monday and 1,200 by 1pm on Tuesday.
Blogging on The Huffington Post UK, Professor Steve Barnett said The Sun's front page amounted to a "shameful distortion of its own polling data".
"The front page juxtaposition of 'Brit Muslims', 'Jihadis' and frightening photo of an Isis murderer is no accident," the University of Westminster communications professor wrote.
"It reflects the warmongering editorial tone of the newspaper, which is apparently intent on exploiting any means at its disposal to persuade its readers that British muslims are - at best - ambivalent about terrorism. Its dishonest use of opinion polling is the Sun's latest weapon of choice in this undeclared propaganda war....
"The truth is, we have absolutely no idea how many of those one in five have 'sympathy for jihadis'."
He added: "Imagine a poll in 1937, in the midst of the Spanish civil war, which asked British voters whether they had sympathy for those who went to join fighters in Spain.
"How would you interpret a figure of 20% who said yes? Were they sympathising with the pro-Franco nationalist forces, or the anti-Franco republican forces? We would not have known."
A Sun spokesman told HuffPost UK the paper was not commenting beyond a strident leader titled 'Face The Facts', published in today's paper.
"Most of our survey, commissioned after the Paris atrocities, probed Muslim attitudes to IS specifically," it said.
"No one agreeing to the statement... was in any doubt which fighters we meant.
"Some on the political Left claim ours was a 'rogue' poll. In fact, the numbers expressing sympathy for jihadists were down on similar survey by the BBC and Sky after the Charlie Hebdo massacre.
"All three polls reveal an undeniable truth. Among British Muslims, a minority - but a substantial one- appear sympathetic to a death cult which is among the most evil in history."
The Sun's poll found a fewer proportion of British Muslims sympathising with those going to join fighters in Syria, after a Sky News poll in March found 28% expressed some sympathy.
Last month, a man was arrested in connection with the death of 82-year-old Palmira Silva, who was reportedly beheaded in her own garden. The Sun was branded "deliberately inflammatory" as people questioned why his religion was relevant, especially given that the police had ruled out any link to terrorism by that stage.
Pizza Express' 'halal secret' screamed the headline. It reported that all the chicken used by the chain was killed in accordance with Islamic law, sparking a race by the press to see who could reveal which other food outlets sold what type halal meat first. This was onstensibly reported as an animal welfare issue but controversy over whether halal-slaughtered animals do suffer more - and the fact Pizza Express already said on its website its chicken was halal - left some unconvinced. So everyone knew about Pizza Express meat being halal, and its on their website, *except* The Sun until today? http://t.co/HGi1t4MWMG— Sunny Hundal (@sunny_hundal) May 7, 2014
Using a mocking pun to discuss a sensitive issue, The Sun said that Channel 4's decision to broadcast the Muslim call to prayer during the holy Muslim month of Ramadan could "inflame tension", which prompted this reply: Channel4's decision 2 air Adhan could inflame tension according 2 Sun "newspaper" but headline "Ramadan a ding dong" doesn't? #sunRamadan— Jammy Dodger (@mrjammyjamjar) July 2, 2013
The Sun reported that London bus driver Arunas Raulynaitis had stopped his bus so he could pray and was mistaken for a "fanatic" because of his rucksack. Five months later, the paper apologised and said the claims were "completely untrue". "Mr Raulynaitis is not a fanatic and he did not ask passengers to leave his bus to allow him to pray," the correction read. "In fact, he was praying during his statutory rest break."
Brave soldiers. Yobbish Muslims. In a fit of tabloid adjectives, The Sun reported Muslims had hounded Afghanistan veterans out of the Berkshire neighbourhood they wanted to rent a house in. Months later, the paper conceded: "Police have been unable to establish if any faith or religious group was responsible for the incident. We are happy to make this clear."
'Thousands of hospital patients are in danger of catching deadly superbugs because Muslim medical students refuse to follow new hygiene rules,' the paper reported. In their book Muslims Under Siege, authors James Jones and Peter Oborne visited Leicester University to see the evidence for themselves. 'Not a single doctor or member of staff we spoke to had come across any problems with hand-washing,' they wrote. 'Dr Paul Symonds, Reader and Consultant Clinical Oncologist at Leicester University, told us: "I personally haven’t seen it. I know of no-one who says they’ve seen it, and I’ve discussed it with our junior staff, nurses, colleagues, and everyone just looks blankly at me with blank incomprehension… the issue has not arisen."'