In a speech to the Commsday Congress in Melbourne on Thursday, Mr Russell said the government-owned company had strayed from its remit as a wholesaler of internet products to telcos which directly provide plans to household and businesses.

"Is NBN 'wholesale-only' when it proactively contacts one of your customers, and directly negotiates a contract that sets out buying commitments and terms of service?" Mr Russell asked.

"Is NBN 'non-discriminatory' when it advocates for end-users to take up a 100 per cent NBN solution, then promotes certain retailers to deliver it?"

"Is NBN 'wholesale only' when it signs contracts directly with end-users to ensure the long-term use of new fibre, when that customer has to enter a separate contract with the retailer?

"Is NBN 'acting in a transparent and accountable manner' when it asks end-users to sign confidentiality agreements, and tells end-users they must seek NBN's consent to discuss contracts with their own retailer?

"In our opinion, the answer to each of these questions is 'no'."

It comes just a day after the competition watchdog slapped the NBN Co, which has a monopoly on fixed-line internet services, with a formal warning for allowing one telecommunications company to see sensitive details about pricing months ahead of its rivals and discriminating between providers.

Mr Russell said the action was a welcome development, but questioned whether it was enough.

He called for the government to issue the NBN Co a new statement of expectations with clear policy objectives, noting its current one was issued three years ago and did not provide guidance about the enterprise market behaviour.

"Because in the absence of long-term policy objectives, NBN's behaviour is being driven primarily by the need to fill a financial hole," he said.

He suggested the updated directives should encourage the NBN Co to prioritise enterprise in under-serviced regional areas instead of using its significantly lower rate of return, made possible by government funding, to undercut competitors in cities.

In addition, he said, the NBN Co should not be able to design tenders with, enter contracts, with negotiate buying commitments or terms of service with, sign confidentiality agreements with or recommend retailers to end-users.

An NBN Co spokesman said in a statement that the company supports the principles of open access and competition. "Business customers have the choice whether to utilise alternative networks or to take advantage of an NBN network offering where available", it said.

"One of the key benefits of the NBN network is retail competition, as customers have a choice of retail service providers supplying services over the NBN network."