Orange is set to overtake BT Cellnet as the UK's second biggest mobile phone operator, and is closing in on leader Vodafone.
Figures to be released on Monday will show that while BT Cellnet has attracted 1.3m subscribers since the start of the year to reach a total of 11.4m, Orange has attracted 2m to reach 11.8m.
Orange has also cut the gap to market leader Vodafone (12.5m subscribers) to around 700,000. Vodafone has attracted only 889,000 new users so far this year.
Demotion to third place could prove costly for Debt-laden BT, which wants to spin off its wireless arm in a flotation.
The numbers show that overall market growth for mobile sales has slowed considerably in recent months.
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