One of the two DJs who made a prank call to the hospital where the Duchess of Cambridge was being treated for an extreme form of morning sickness has returned to the airwaves.

Australians Michael Christian and Mel Greig sparked outrage in December when they were transferred to Kate's ward in a phone call to the King Edward VII's Hospital in which they posed as Prince Charles and the Queen.

They were suspended by 2Day FM in Sydney after the nurse who answered the phone committed suicide.

Mr Christian appeared on sister-station Fox FM in Melbourne. His return follows an announcement by British prosecutors that the DJs would not face charges in connection with Jacintha Saldanha's death.

Ms Saldanha's family said relatives have many unanswered questions about the events that led to her death.