Almost one in five Americans believe that Barack Obama is a Muslim, according to a new poll, despite his public statements about his Christian faith.

The survey by the Pew Research Centre found that 18 per cent now say the US President is a Muslim, up from 11 per cent in March 2009. Only about one-third of adults (34 per cent) say Mr Obama is a Christian, down sharply from 48 per cent in 2009. Forty three per cent say they do not know Mr Obama's religion.

The survey was completed early this month, before Mr Obama's recent comments about the proposed construction of a mosque near the former site of the World Trade Centre, which have landed him in political hot water.

The President has said he believes Muslims have the right to build an Islamic centre there, but refrained from taking a position on whether or not it should actually be built two blocks from Ground Zero.

The issue has become politically charged ahead of congressional races in mid-November, with Republicans accusing Mr Obama of being out touch with mainstream America.