Clear Channel Communications, the largest radio station group in the US, gave an upbeat assessment of its strategy to reduce the amount of advertising airtime, saying its "less is more" campaign was already working.

Nevertheless, there was no growth in its radio business - its biggest division - in the fourth quarter of 2004, with revenues flat versus the fourth quarter of 2003.

The outdoor advertising business performed better, with 12 per cent earnings growth in the fourth quarter. Live entertainment, which had one of its worst years in 2004 with many concerts and events cancelled, saw a fall in revenues of 12 per cent.

"Clear Channel's core radio business will remain challenged through this transition year, and its entertainment unit should remain unpredictable," said Mr Peter Mirsky, analyst at Oppenheimer, in a note.

Clear Channel shares were down 2.5 per cent at $33.06 after the earnings were reported.

The shares have fallen sharply in the past year amid concerns about the lack of growth in the traditional radio business. The company is reducing the number of 60-second advertising slots and replacing them with 30-second slots.

The company posted a net loss of $4.67 billion (€3.5 billion) following a write-down of the value of its radio licences.

The loss comes a day after Viacom posted a record $18.4 billion quarterly loss after slashing the value of its Infinity Broadcasting unit.

Profit at Clear Channel, excluding the effect of the write-down, rose to $214.3 million, or 37 cents a share, from $187.2 million, or 30 cents.