BT'S mobile phone business BT Wireless has announced a fall in customer numbers after deciding to adopt a tighter definition of so-called "active users".

The company has excluded from its figures pre-pay customers who have not used their phones for at least three months .

Its total customer base, across the UK, Germany, the Netherlands, Ireland and the Isle of Man, was 16.1 million after the first quarter, to the end of June, compared to 16.9 million three months earlier.

BT said that if the same counting procedure had been used for the three months to April, total customer numbers would have grown by 3.1 per cent, or 492,000.

Peter Erskine, BT Wireless's chief executive, said the move to adopt a stricter definition of customer numbers set a "new benchmark" for the industry.

He added: "The change in our reporting base is a logical and important step to help our stakeholders clearly understand the underlying trends both in our business and the wireless market as a whole."

In the UK, BT Cellnet's customer base rose by 301,000 in the first quarter to 10.9 million on a like-for-like basis.

This confirms it has lost the number two spot in the market to Orange, which has call centre operations across the North-East, including a major site in Darling-ton.

Last week, Orange said its active customer base grew to 11.9 million.

Customer numbers at BT Genie, BT Wireless's mobile Internet portal, rose 41 per cent in the first quarter to 5.5 million.

BT hopes to spin off BT Wireless later this year as part of a programme to slash its debt mountain.

In a separate move, BT announced two more appointments to strengthen the future company's management team.

Andrew Sukawaty, partner and president of cable television group Callahan Associates, will join as deputy chairman, while Paul Myners, chairman of Gartmore Investment Management, will become a non-executive director.

Mr Myners recently completed the Myners Report - a review of institutional investment - for the Treasury.