ITV was bracing itself for a long, cold winter on Wednesday, with a bleak prediction that advertising in January could fall by between 12 and 18 per cent on its flagship channel.

The forecast reflects the gloom on the high street, since retailers are the most important source of advertising for ITV, and looks beyond the Christmas shopping rush, which brings with it a fillip in seasonal television ads.

The prediction, circulated internally on Tuesday, reflects the fact that retailers increasingly are taking a short-term view of booking advertising. “People are just booking from week to week,” one ITV insider said. Indeed, at one point ITV feared that ITV1 bookings in December could be down by as much as 20 per cent, but the figure has improved, reflecting what is described in the industry as “late money”.

December bookings are expected to be down by 15 per cent on ITV1, home to Coronation Street and Emmerdale, even though some late sales campaigns by retailers have helped to lift that figure.

In the first half of the year retailers accounted for £132 million of revenue, a rise of 17.7 per cent, as shop owners battled to persuade consumers to keep spending. Now, however, the collapse of Woolworths and MFI has introduced a new concern - where retailers in administration are no longer able to pay their bills. Moreover, it is expected that concern about the financial health of retailers will become even more acute next month, when it will become clear who has had a bad Christmas, meaning that some advertisers will no longer be granted credit.

Growth at ITV's digital channels will temper the overall advertising decline and total advertising revenues at ITV are expected to be down between 6 and 10 per cent in January, with the commercial broadcaster broadly hanging on to its overall share of the shrunken television advertising pie.

ITV1's overall audience share has dipped from 19.3 per cent to 18.6 per cent so far this year, despite the popularity of The X Factor on Saturday night, but Channel 4, its principal rival for advertisers, has also lost ground, falling from 8.7 per cent to 8.2 per cent.

ITV bookings act as a proxy for the wider advertising market. National newspaper owners privately are expecting to begin next year down by as much as 15 per cent. When Martin Morgan, the chief executive of Daily Mail and General Trust, owner of the Daily Mail, was asked whether he expected the start of 2009 to be extremely tough, he replied simply: “Yes”.

The broadcaster's shares rose 2p to close at 36p on Wednesday.

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