In a statement, Telstra said it was happy for the feedback.
"The ACCC has reported on some gaps in our systems where access to wholesale customers' information could be better protected," it said. "We proactively identified these gaps ourselves and we are investing significantly in our systems to close them."
Telstra stressed that the security gap identified by the ACCC had not been exploited.
"The report includes no evidence to suggest our retail staff have used wholesale customer information to gain an unfair commercial advantage."
Also, the telco said that it delivered equivalent services between retail and wholesale most of the time.
"Last year we had more than 100 million interactions with our customers and end users on the Telstra network and we performed very well in delivering equivalence across all these interactions," it said.
"Nonetheless, we acknowledge the gaps in our systems and are working to fix them."
Competitive telcos represented by the CCC disagreed with Telstra's claim that there was only an occasional problem with line tests wrongly reporting wholesale ADSL service was not available.
The CCC said the admission confirmed years of repeated complaints from CCC members.
"Telstra has finally admitted that it has been rejecting applications for broadband from customers who wanted to use anyone but Telstra, simply because it was not testing their lines properly," a CCC spokesman said.
"By contrast, if the order came from Telstra Retail, surprise, surprise, a more thorough test was applied. As a result, consumers were told they could not get broadband from a competitor, but told they could get it from Telstra."
The CCC said it is waiting to hear from the ACCC on the matter.
"This is further evidence of the importance to deliver genuine structural separation of the access network by ensure that the NBN is owned and operated completely independently of any retailer," the CCC spokesman said.
"It is also crucial that the ACCC demands Telstra remedies this unfair treatment quickly, and not in six months as Telstra proposes."
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