Newspaper reports have suggested the anti-trust regulator is calling for reductions on the heavy price of calling other networks, which typically costs over 55p per minute.

Calls could be cut to half their current price levels over three years, following a 12 month investigation into the so-called "termination charges" between different networks.

The ruling could spell bad news for mobile phone groups, after analysts suggested the full benefit of the reductions would be passed on to the consumer and dampen revenues for operators.

Embarrassment

The Financial Times newspaper said the Competition Commission is expected has called for a one-off price cut of 15%, followed by reductions of 14% over the next three years.

The Competition Commission's ruling would be implemented by the telecoms regulator Oftel from April.

The irony of the reduction will not be lost on mobile phone groups who referred the case to the Competition Commission themselves.

They had objected to Oftel's call for a reduction of inflation minus 12% over four years.

Oftel told BBC News Online that it had received the Commission's report and that it was now being looked at by ministers.

It said details of the findings and any decisions would be made in the next one or two weeks.

Multimedia setback

But investors already feared the worst, with shares in Britain's major mobile phone operators slipping on the news.

Mm02, the former mobile arm of BT Group, is considered to be the most vulnerable as it generates two-thirds of its calls in the UK.

Analysts suggested any fall in revenue would hamper plans to invest in new multimedia technology and gain the edge on rivals.

MmO2 shares fell 5%, while rivals Vodafone and Orange lost 2% and 3% respectively.