Earlier this month, Channel 5 announced that Van Outen would co-host the celebrity news show with Matt Johnson.
However, Van Outen has now pulled out of the programme, which is due to premiere on Monday.
In a statement, Channel 5 said: "Due to other contractual commitments, Denise Van Outen will not be presenting OK! TV. Both parties wish each other the very best."
OK! TV is scheduled to begin on Monday at 6.30pm on Channel 5.