"We are very concerned about these amendments .... We are also willing to try and work (with the government) to amend these amendments," chief executive Paul O'Sullivan told a business lunch in Sydney.

The government this week proposed to amend legislation to allow the National Broadband Network Company (NBN Co) to sell services directly to big businesses like banks and utilities, who are key customers of top phone provider Telstra Corp and Optus.

The A$35 billion NBN, a key election promise of the ruling minority Labor government, aims to use Telstra's fixed-line assets for the network.