More than one quarter of a million contract customers joined O2 during the first quarter of this year.
Up 13 per cent year on year, 251 000 contract customers joined the operator during the first three months of 2013, which O2 said was its highest number of additions in the first quarter for four years.
O2 now had 12.15 million contract customers, which made up 53 per cent of its total mobile customer base, Mobile News reported.
The total mobile customer base was up 3 per cent year on year, to 22.9 million mobile customers at the end of the quarter, O2 said. However the operator lost about 205 000 pre pay customers, due to seasonal factors, it said.
Revenues were â¬1,605 million ( £1,361 million) for the first quarter, which was down 4.8 per cent compared with the same quarter in the previous year. Excluding mobile termination rate cuts and roaming regulation, revenues would have decreased by 1 per cent year on year.
O2 said its Refresh tariff, which launched last month and allowed customers to get new phones without having to pay out an airtime contract, was chosen by nine out of 10 new customers selecting the plan over other pay monthly deals.
Its 4G service was coming in summer, O2 said.