Telstra chief executive Andrew Penn has blamed the national broadband network (NBN) for potential job cuts as the phone company attempts to transform itself into a tech business.

As he unveiled a 5.8 per cent fall in half-year net profit to $1.7 billion and a sharply lower dividend on Thursday, Mr Penn flagged "reducing and disappearing" jobs in parts of the business, in large part because of the NBN.

Telstra has dropped its dividend to 11 cents.

While Telstra was "always sensitive to anything that we're doing that has an impact on jobs [...], we do need to increase the efficiency of the business, the productivity of the business, because ultimately that’s what’s going to make us successful," he said.

This meant changing the workforce of the company, particularly due to the NBN, as Telstra moved into new technology and redefined its role in the market, he said.