The Independent on Sunday newspaper had reported European football's governing body was considering expanding the tournament to have an event that could include Brazil, Argentina, Mexico and Japan.
A UEFA spokesman said tonight: "We can confirm that UEFA is not aware of the plans mentioned in the story in the Independent."
There is precedent for continental championships inviting outsiders, with the United States, Mexico and Costa Rica having competed in South American tournament, the Copa America.
FIFA would regard any such revised format of the European Championship that brings in big-name teams from outside as a threat to the World Cup, which is its biggest source of income.
The initial story also led to further talk of a rift between FIFA president Sepp Blatter and his UEFA counterpart Michel Platini.
The pair are understood to have strained relations, and the former has come under fire from Premier League clubs in England over the possible switch of the schedule of the 2022 World Cup in Qatar from the summer to the winter.