According to Barb figures, ITV's share of viewing in all TV homes was just 22.4 per cent - down from 25.8 per cent on last year and 24 per cent on the previous month. In comparison, multichannel's share of viewing grew to 21.7 per cent, an increase of 8 per cent on last year.
Even more startlingly, there were 11 days in July when ITV was beaten by viewing of the non-terrestrials. Its worst day was 25 July, when its share of audience slumped to just 17.5 per cent after viewers were turned off by back-to-back peaktime shows hosted by Carol Vorderman.
Unsurprisingly, Big Brother contributed to a marked improvement in Channel 4's share, while Channel 5 continued to grow and commanded a 6.5 per cent share.
The news comes at a difficult time for ITV - it is estimated that around 60 per cent of TV deals are up for re-negotiation, and these audience figures will not be lost on TV planners.
Channel 5's deputy chief executive, Nick Milligan, said: "The planning lag dictates that revenue does not follow audiences until the following deal season. Given the considerable variance of each station's audience supply, this is going to be one of the most demanding negotiation seasons."