Industry sources have indicated that the company, which is headed by former FM104 chief executive Dermot Hanrahan, believes that O'Brien will choose to sell FM104 if the authority orders him to divest one of his radio interests.

It expects that O'Brien will be forced to choose between his two largest Dublin stations, 98FM and FM104, to satisfy the authority's competition concerns.

Although FM104 has historically been the more successful of the two stations, Vienna believes that O'Brien feels a strong sentimental connection to 98FM, which has been the cornerstone of his business empire since 1988.

Meanwhile, industry sources have indicated that it could prove difficult for O'Brien to obtain a significant return on his new investment, given the high price that he paid for them.

It is understood that the second-highest bidder for the stations, Vienna, withdrew from the bidding process because it felt it had become economically impossible to justify the transaction. Its final bid was 193m while the third-highest bidder TV3's final offer was 180m.

However, Emap's discussions with TV3 ended on Friday morning and it is unclear whether TV3 would have upped its bid if it had become involved in more advanced negotiations.

But industry figures have indicated that management at the independent TV station regard the price paid by Communicorp to be excessive.

"For the transaction to work, O'Brien is going to have to strip out costs, make people redundant or sell something on, which could cause problems with the BCI in terms of its requirements governing the sustainability of the licences, " said one source.

Some sources have indicated that Communicorp's new acquisitions may also hamper O'Brien's ambitions to take over the country's largest newspaper group, Independent News & Media (IN&M).

O'Brien's current 8.6% stake in IN&M, which owns 29.9% of this newspaper, is also likely to come under intense scrutiny from the Competition Authority when it examines the purchase of the stations.

One respected competition expert who asked not to be identified said that it was logical to assume that O'Brien's radio deal would make it much more difficult to acquire control of IN&M because the Competition Authority had to consider the acquirer's interests in all forms of media.

If the deal is approved without alteration, O'Brien will secure 45% of the Dublin market compared with RTE's 44.5% stake, based on the latest JNLR listenership figures. He would also have control of the two independent stations, Today FM and Newstalk, with the largest national reach.