Vodafone's Chris Gent says average revenue figures are 'stabilising'

As a result, the average revenue per user - or ARPU - measure has become more significant than the number of customers in order to measure the success of mobile phone firms.

Orange's ARPU fell from �280 to �246 in the UK, and from 426 euros to 392 euros in France.

But it is now concentrating on the more lucrative contract market, as opposed to prepay phones, and said it had begun to see the benefits in the UK in recent months.

"In the UK we have achieved the second successive quarterly increase in average customer revenues," said deputy chief executive Graham Howe.

"Despite the rapid growth of our customer base we may be approaching, sooner than expected, the point when overall average revenues start to grow."

Vodafone said its annual ARPU dropped seven pounds to �274 in the UK over the October to December period.

It also fell back in Germany but held firm in Italy.

Vodafone's chief executive Chris Gent said that adjusting for seasonal factors, ARPU "continues to stabilise."

Subscriber comparisons

Orange now claims it has toppled Vodafone as the UK's leading mobile operator.

In defining customer numbers Orange said it excludes "any customer who does not make at least one outgoing call or receive fewer than four incoming calls a quarter."

It said if it adopted "the less stringent definition of other operators" its UK numbers would be 656,000 higher.

Meanwhile Vodafone says it defines active customers as those "who have made or received a chargeable event in the last three months."

In the UK, Vodafone said 84% of its customers were defined as active - implying an active UK customer base of about 11.1 million.

On Monday, Virgin Mobile, the mobile phone group which is a joint venture between Virgin and Deutsche Telekom's One2One, said it had gained 1.5 million customers in the two years since formation.

Analysts say the venture has managed to increase its user base relatively quickly as it has targeted the prepay market, which other operators are increasingly turning away from.