A write-down of the national broadband network would help telcos boost profit margins, competition regulator Rod Sims says, but warned it remains unclear how much would flow through to consumers in the form of retail price savings.

With Labor suggesting a NBN write-down is increasingly likely, the chair of the Australian Competition and Consumer Commission said telcos agitating for a cut to wholesale prices were doing so because they wanted to ease pressure on margins.

Competition regulator chair Rod Sims. Credit:Nic Walker

"You have no idea whether it will flow to consumers. Listening to telcos, they want to keep a decent chunk of that ... I suspect some would flow through to consumers but it would be a mix of the two," he said.

"But I can’t tell you what that mix would be. The telcos, they want to make more money. And that’s perfectly legitimate. I’m not criticising them for that."