NBN chief executive Bill Morrow will quit his role by the end of the year, ending four years heading the rollout of the national broadband network.

A global search will now take place to find a replacement for Mr Morrow, who said in a note to staff it was “with a heavy heart” that he was announcing his decision to leave in order to pursue the next chapter of his career.

“At times my role at NBN has been challenging, relentless, and yes, sometimes frustrating but never has there been a time that I wasn’t proud to be a part of the NBN team,” Mr Morrow said in the note.

Mr Morrow has given no details of his next move, saying in a statement it was the right time to hand over leadership for the next phase of the NBN.

Mr Morrow was brought in as CEO of NBN Co in 2014, coming across from his post as CEO of Vodafone Australia, where he had overseen a turnaround of the telco.

He replaced inaugural NBN CEO Mike Quigley.

NBN chairman Ziggy Switkowski said Australia had been fortunate to have Mr Morrow lead the NBN project, which now covers about 6.5 million homes.

“While we will be sorry to see him leave, Bill has built a resilient, performance-driven organisation which will build on his legacy,” Dr Switkowski said.