Eircom has said its revenue fell by 3% to €313m in the first three months of its financial year.
The telecoms group said its fixed line business had fallen during the three months to the end of September, which more than wiped out the gains it made in the mobile market.
Mobile revenue for the three month period rose by 2% compared to the same time last year.
Earnings before tax fell by 6% to €114m as a result of planned investment in subscriber growth.
Eircom also reported continued growth in broadband, with an 8% rise in broadband connections to bring it to 731,000.
This marked an increase of 13,000 customers in the quarter and was driven by both its consumer and business retail divisions as well as its wholesale division.
In its mobile division, the group's customer base returned to growth, with customers rising by 8,000 from the same time last year and by 10,000 in the previous quarter, to reach a total of 1,065,000.
It noted that that the higher value post-paid segment grew by 60,000 - including mobile broadband - compared to the same time last year.
The company also said it was proceeding with the corporate restructure of its operating company structure, which was outlined earlier this year.
It said that while it will not impact on its operations, customers or business partners, the reorganisation will provide the group with greater flexibility for the future.
During the quarter, Eircom's next generation fibre network passed the one million premises milestone and it said it was on course to deliver a fibre footprint of 1.6 million premises by June 2016.
"We have maintained our momentum in the first quarter, through focused commercial execution and continued investment in our fixed and mobile network," commented newly appointed Eircom CEO Richard Moat.
"The rate of revenue decline has slowed significantly, an encouraging sign of stabilisation, helped by two consecutive quarters of mobile revenue growth. Our bottom line performance remains in line with expectations, following a decision to make commercial investments this quarter that will deliver long term growth," Mr Moat added.