More Australian homes and businesses are connecting to higher-speed national broadband network services, with NBN's second fastest package making up more than a quarter of all plans.

The consumer watchdog says connections on NBN Co's 50Mbps plan have increased five-fold since December, after the company temporarily discounted pricing - a move which has since been superseded by new bundles.

The number of 50Mbps services being acquired from NBN Co increased from 158,959 to 989,360 in the three months to March 31, as a result of the December discount which slashed the cost of a 50Mbps plan to the price of a 25Mbps plan.

NBN Co started offering new wholesale pricing options at the beginning of May, though new customers will be offered the discounted prices until October in order to help them transition to the new bundles.

Australian Competition and Consumer Commission chairman Rod Sims said the number of connections is a "remarkable shift", with nearly one million customers now using the faster speed plan.

"This is good for consumers who can enjoy the benefits of higher speeds," Mr Sims said.

"However, we would expect that with more consumers on higher speed plans, retailers will continue to provision enough CVC (bandwidth) to ensure a continuing good customer experience, particularly during the busy evening periods."

NBN Co on Thursday said it had more than doubled its revenue in the first nine months of the financial year, thanks to solid construction progress and a surge in the number of NBN connections.

Revenue in the nine months to March 31 of $1.4 billion was up from $665 million a year ago, with two million more premises ready to connect.

There were 6.5 million premises ready for connection at March 31, and 3.7 million active connections across the network, up 1.7 million from a year earlier.

NBN chief executive Bill Morrow, who will step down before the end of 2018, said the company had made significant improvements to its customer services, but there was more to be done.

He said the board continues to search for his replacement.