As many as one in five Americans think wrongly that President Barack Obama is a Muslim, indicating a significant increase in the number of such people since his inauguration in January 2009.
At the same time, the number of people who now correctly identify Obama as a Christian has dropped to 34 per cent, down from nearly half when he took office, according to new Pew Research Centre survey.
Among those who say Obama is a Muslim, 60 per cent say they learned about his religion from the media, suggesting that their opinions are fuelled by misinformation, says the poll.
The poll was conducted before he expressed support for the Muslims' right to construct an Islamic cultural centre and mosque near the 9/11 terror attack site in New York.
While some suggest such a perception could pose serious political danger for the White House as the debate over his remarks continues, others say the shifting attitudes about the president's religious beliefs could also be the result of a public growing less enamoured of him and increasingly attracted to labels they perceive as negative.
In the Pew poll, 41 per cent disapprove of Obama's job performance, compared with 26 per cent disapproval in its March 2009 poll.
More than a third of conservative Republicans now say Obama is a Muslim, nearly double the percentage saying so early last year. Independents, too, are now more apt to see the president as a Muslim: Among independents, 18 per cent say he is a Muslim, up eight percentage points.
Obama was born to a Kenyan father and an American father and was brought up by his maternl grandparents in Hawaii because his father, who was also called Barack, left for Africa when Obama was just two. He has said in his autobiography that his grandfather, Hussein Onyango Obama, was a Muslim.
Expressing dismay over the poll results, White House faith adviser Joshua DuBois blamed "misinformation campaigns" by the president's opponents.
"While the president has been diligent and personally committed to his own Christian faith, there's certainly folks who are intent on spreading falsehoods about the president and his values and beliefs," he said.
The president's Christian faith plays an "important part" in his daily life, DuBois said pointing to six speeches on faith that obama has given in which he talked about his beliefs. But Dubois said coverage of Obama's Christianity has been scant compared with news about the economic crisis, legislative battles and other issues.