The Chris Tarrant-hosted programme launched in 1998 and pulled in huge audiences at its peak. However, The Mirror claims that falling ratings have prompted the broadcaster to scrap the show.
Following the success of the live edition screened over Christmas, ITV is said to be keen to develop more of the special episodes in order to create "event" TV.
"We are looking to do fewer shows but make them higher profile," a source told the paper. "The appetite at the moment is for big specials while the audience has drifted away from the run-of-the-mill instalments featuring ordinary punters.
"It's still a popular brand but we need to make sure it remains fresh and relevant. There's a realisation that having Millionaire on every week for eight weeks perhaps isn't the way forward anymore."
The show introduced a revamped format, which included fewer questions to win the top prize, in 2007. Further changes made last year also saw the Fastest Finger First section scrapped.
"The changes that were made last year haven't necessarily worked," the insider admitted.
An ITV spokesman added: "The first ever live edition over Christmas attracted 6.9 million viewers. We are talking to producers, Sony Pictures, about future episodes."