NBN board member and former Telstra executive Justin Milne is expected to be appointed the new chair of the ABC by the Turnbull government later this week.

Mr Milne will succeed former NSW chief justice James Spigelman in the prestigious role when his five-year term officially expires at the end of the month.

Mr Milne has been a long-time friend of Prime Minister Malcolm Turnbull since they worked together at internet service provider Ozemail in the 1990s.

The chair of the ABC is unusually the prerogative of the prime minister with input from the minister for communications.