Advertisers' trade body ISBA and agency trade body IPA have expressed concern that ITV, Channel 4 and Five will use the abolition of airtime trading rules to increase the price of advertising on TV.
Ofcom announced yesterday that the three public service broadcasters would no longer be forced to sell all their ad minutes and would be able to insist agencies and advertisers buy ads on bundles of channels from 1 September.
Bob Wootton, director of media and advertising at ISBA, said: "The concern for the UK’s television advertisers is that broadcasters might withhold airtime to force prices or begin to leverage the sale of more generic airtime against stronger slots, like those in primetime and special viewing events.
"ISBA hopes that Ofcom’s argument, that there are sufficient economic incentives in the market to prevent broadcasters from withholding airtime, is proved true in the marketplace."
The IPA also said it was profoundly disappointed with the decision. Geoffrey Russell, the organisation's director of media affairs, said: "We fundamentally disagreed with Ofcom's premise that real power in the TV market had been diluted over time.
"While the regulator’s theoretical modelling may have suggested that it would not be to broadcasters’ advantage to abuse any new freedoms, we drew on practical experience to indicate not only that airtime manipulation was likely, but how this might take place."