Just 300,000 tuned in to the new channel's soap Family Affairs at 6.30pm and the first broadcast of its nightly entertainment gossip show Exclusive! at 7pm. The same number watched its wildlife programme Wildlife SOS, according to unofficial figures.
Its first nine o'clock film - on which so much of the channel's audience strategy is based - was Losing Chase with Helen Mirren, and was watched by 900,000 viewers.
The channel's Easter Monday night viewing share was just 2.7 per cent, compared with 5.8 per cent on its launch night on Sunday.
A Channel 5 spokeswoman said: "These are in line with our expectations. From our point of view the ratings are unrealistic because many people are still tuning in and the other channels are using their big programmes against us.
"We want to wait for another two weeks for a more accurate picture to emerge."
BBC1 won the Easter ratings battle, taking a 45.5 per cent share on Monday night compared with ITV's 32.7 per cent. The top-rating programme was the second of two EastEnders episodes, which was seen by 15.3 million viewers.
It was followed by the one-off special, Before They Were Famous, hosted by Angus Deayton, which picked up 14.2 million viewers at 9pm. ITV's Coronation Street came in third with 12.7 million viewers.