Agencies, all of which have now signed up to the Contract Rights Renewal procedure, are expecting the month's revenues to be down by about 4 per cent, with all TV stations hit by the slump.
Significantly, this could mark the first time that ITV's share of TV revenue has slipped below the 50 per cent mark, even though it is expected to outperform the growth in the market in February. Shares in the merged ITV plc began trading on Monday.
Broadcast directors are baffled by the predicted decline, particularly as Easter is in early April this year. Normally, this would lead to additional money coming into March as advertisers seek to capitalise on the forthcoming Bank Holiday break.
John Overend, the investment director at PHD, said there was no single category responsible for this decline. "Everyone's scratching their heads wondering why it is so poor. It should be good because of the early Easter."
In January, the TV market was up 2 per cent and in February it is expected to grow by 4 per cent, with ITV, buoyed by audiences tuning into I'm a Celebrity ... Get Me Out of Here, taking 5 per cent more ad revenue than it did in the previous year.
Despite ITV appearing to bear the brunt of the March decline, Overend says this is because it is the market leader and not because it is performing particularly poorly.