Citigroup's media analysts pointed out that while the red-top Sunday Mirror was the most obvious substitute, the Mail brand was becoming increasingly associated with the kind of celebrity gossip that was the staple fodder of the News of the World.
The Mail on Sunday is 75% bigger in circulation terms and, from next week, becomes the new biggest Sunday paper. "That will arguably make it an increasingly attractive proposition for advertisers," Citi said.
Stockbrokers Liberum Capital argued the Sun on Sunday would not be launched for several months, but others said Murdoch may want to launch far sooner to prevent his readers getting too used to taking other papers.
Trinity Mirror and Express Newspapers declined to comment.