For the quarter to 31 March 2012, Optus's operating revenue declined 1.1 per cent year on year to $2.296 billion. According to SingTel, the result reflects the "continued intense competition and the mandated reduction in mobile termination rates from 9 cents per minute to 6 cents from 1 January 2012."

Optus also recorded a decline in its mobile-related operating revenues of 3 per cent and a decline of 2 per cent in its mobile service revenue to $1.23 billion.

Detailing , SingTel said Optus added some 82,000 post-paid customers during the quarter and maintained its pre-paid customers numbers bringing Optus' total customer base to 9.49 million as at March 2012.

Quarter on quarter Optus grew its 3G customer base to 6.63 million. 3G-based wireless broadband customers grew 6 per cent, or 26,000 customers, to 1.58 million.

In February this year, net profit for the three months to December 31 rose just $8 million to $177 million, compared to the prior corresponding period.