"If you are asking if they are having an affair, the answer is no," the spokesman told The Hollywood Reporter, adding Blair would not publicly comment further on the Murdochs' divorce proceedings, which began in New York Thursday.
Media speculation about the cause of the split has focused on Wendi Murdoch's relationship with powerful men, including Blair, 60, who is married.
Wendi Deng Murdoch, 44, was born in China and attended college in the United States. She met Rupert Murdoch, now 82, while she was working for his Star TV operation in Hong Kong and married him on a yacht in New York Harbor in 1999. They have two daughters -- Grace, 11, and Chloe, 9.
Rupert Murdoch's representative said he filed for divorce from his third wife because the "relationship between husband and wife has broken down irretrievably."