O2 continued to shed home broadband subscribers during the third quarter of 2012.
Latest figures published by the service provider reveal a loss of 22,500 fixed-line customers between July and September this year.
This leaves the firm with a total of 579,500 broadband subscribers in the UK - more than 45,000 down on the equivalent point in 2011.
The rate of attrition increased during Q2 2012 - 15,800 customers were lost during the second quarter of the year.
Indeed, subscriber levels have continued to fall since reaching a peak of 671,600 in December 2010.
O2 and sister firm Be Broadband still do not offer fibre broadband services, which may be influencing some customers to switch provider.
Among the major UK broadband providers, they are the only firms not to offer super-fast internet services.