Britain's Prime Minister David Cameron says FIFA president Sepp Blatter must resign and ``the sooner that happens the better.''

Asked about the FIFA scandals at a joint press conference in Berlin with German Chancellor Angela Merkel, Cameron said it was ``unthinkable'' that Blatter was the right person to take the world soccer body forward after this week's corruption accusations.

Cameron added, ``Frankly, what we have seen is the ugly side of the beautiful game.''

Merkel called for FIFA to make a clean break with corruption but stopped short of saying that Blatter should resign.

Blatter is running for a fifth, four-year term as FIFA president later Friday against challenger Prince Ali bin al-Hussein of Jordan. Most European nations back the prince but Blatter is expected to win anyway. (AP)