The two crime thrillers, both written by brothers Harry and Jack Williams (The Missing), went head to head at 9PM for a fourth week in a row.
In the opening episodes, there was a clear winner with Liar coming out on top with 5.3 million viewers to Rellik's 3.6 million. The next week the gap between the two shows widened as Liar increased to 5.4 million as Rellik dropped right down to 2.1 million viewers.
Last night as both shows aired their fifth episode, Liar hit a series high of 5.8 million viewers on ITV.
Rellik on the other hand continued with 1.5 million viewers in the same slot.
Liar couldn't quite outdo the soaps which topped the night once more. Coronation Street scored the best numbers with 7.3 million and 6.9 million for its two episodes.
EastEnders meanwhile continued with 5.6 million viewers, while Emmerdale was just ahead with 6.6 million.
Earlier in the day, The Chase had 3.1 million viewers to Pointless' 2.8 million.