The first signs of a cold season for advertising markets appeared on Thursday with warnings that some retailers have cut marketing budgets.

Analysts warned that this would worsen the financial situation for UK commercial broadcasters such as ITV and Five, which is owned by German broadcaster RTL.

The harbinger of cold winds came in a trading update by Media Square, the communications and marketing group, which said it expected its first-half, like-for-like revenues to be about 5 per cent down on 2007, partly reflecting "cutbacks by a number of ongoing clients who have reduced their marketing spending".

Those clients include financial services companies, which are already known to be cutting back. For the first time, however, retailers are also among those cutting their advertising budgets.

Vincent Létang, senior analyst on advertising for the consultants Screen Digest, said: "Financial services have been sluggish all year, but if retail is falling into that category as well, that is extremely bad news. It doesn't come as much of a surprise, but it will accelerate the crisis."

Mr Létang said in a note to clients this week that "the fact that the retail sector is one of the few to hold and even increase advertising spending this year, can be analysed as good or bad news.

"It is good news in the short-term as retail is a key client sector; however it is a concern in the mid-term to depend on a sector in such a delicate situation. Suffering increasingly tough high street sales, retailers may at some point cut their advertising spending and that would make television trading even much worse."

Paul Zwillenberg, a partner of the strategy consultants OC&C, said: "The UK is in the eye of the storm right now, but we are seeing a whole lot of very different trends in different sub-sectors of the economy.

"That has everything to do with factors from current trading, to the amount of debt in their businesses."

In its past results, ITV said net advertising revenues for September would be down 20 per cent year-on-year, although that was partly a result of a strong performance in the same period in 2007, when it was broadcasting the Rugby World Cup.

One company not cutting back on advertising budgets is Premier Foods, which is to begin a £9m campaign to revive its Hovis bread brand this autumn.