Let It Shine premiered to an audience of 6.3 million viewers between 7PM and 8:25PM back on January 7 before dipping to 5.3 million viewers for the past two weeks.
However the fourth episode last night saw a rather sudden drop with the show falling almost a further million viewers to 4.6 million.
The Voice UK, which used to air on BBC One, made its debut on ITV for series six with its least watched launch to date at the start of the month.
An average of 6 million viewers (including ITV+1) tuned in, putting it behind Let It Shine.
However while Let It Shine has shed viewers over its run so far, The Voice UK has stayed strong. This weekend's episode had 5.6 million, up 200,000 on last weekend, making it a million viewers clear of its BBC One rival.
What's more, The Voice UK peaked with 6.5 million viewers once Let It Shine had finished, suggesting that the 20-minute overlap between the two shows may well be denting the ITV show's average audience notably.
Meanwhile, earlier in the evening on BBC One yesterday, Pointless had 4.8 million viewers - the same as last week - while after Let It Shine Casualty dipped 500,000 on last Saturday with with 4.3 million viewers.
Drama series Taboo has also continued to decline, now down to 3.4 million viewers, 1.4 million below the launch three weeks ago.
Over on ITV, Ninja Warrior UK jumped 100,000 viewers week-on-week to 3.5 million while Through the Keyhole with Keith Lemon was steady with 3.2 million viewers.