The telecommunications sector fears a return to the ways that resulted in Telecom being fined a record $12 million.
The High Court in Auckland imposed the fine on Tuesday after earlier finding that Telecom had breached the Commerce Act between 2001 and 2004.
The penalty follows a long-running dispute involving allegations that the telecommunications giant denied competitors fair access to internet connections.
Telecom charged competitors disproportionately high prices for wholesale access to what are known as data tails.
As part of the Government's $1.3 billion rollout of ultra-fast broadband, there is a planned 10-year regulatory holiday for ultra-fast broadband operators.
It would stop the Commerce Commission from investigating or regulating prices.
Telecommunications Users' Association chief executive Paul Brislen says if the commission is powerless to act, the industry will surely return to the anti-competitive practices of the early 2000s.
Internet NZ and TelstraClear say that will almost certainly happen.
Mr Brislen says it has taken too long to hold Telecom to account and the fine is 10 years too late.