Mel Giedroyc and Sue Perkins have turned down hosting The Nightly Show because of their "busy schedule".
The new ITV comedy programme sees a different presenter front the show every week for its eight-week run.
"We were approached to take part in the series, however, due to our busy schedule we were unable to make the dates work," the duo said in a statement.
"We do wish the team all the best with the remainder of the series."
Boost in figures
The announcement comes after the show initially struggled with ratings and received poor reviews from critics during its first week.
The opening episode, hosted by David Walliams, was watched by 2.9 million viewers on Monday (27 Feb), but that had dropped to 1.2 million by the following Friday.
However, things now seem to be improving slightly.
John Bishop is in charge this week, and viewing figures of the show have started going up again - with an average of 1.4 million tuning in on Tuesday and 1.6 million on Wednesday.
Walliams previously said The Nightly Show replacing the News At Ten was partly what had contributed to the show's troubles.
"Because they moved the news, I think people were sort of angry about that," he told BBC Breakfast.
But, he added: "I think the problem was ITV News was not getting many viewers for ITV so they wanted to try something different."
Davina McCall and Gordon Ramsay have been confirmed as hosts of The Nightly Show for the next two weeks.
An ITV spokesman confirmed to the Radio Times that Mel and Sue were approached to host the show but stressed they had not been committed.
"Mel and Sue were never signed to present The Nightly Show," the spokesman said.
"The production team undertook discussions with them about the possibility of presenting a week but due to their hectic schedule this wasn't possible."