The Australian radio station which approved an "appalling" prank call to the Duchess of Cambridge humiliated nurses in a tragic incident that should never be repeated, a letter warns.

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"It was extremely foolish of your presenters even to consider trying to lie their way through to one of our patients, let alone actually make the call," King Edward VII hospital Chairman Lord Glenarthur wrote.

He sent the scathing letter to bosses at the radio station behind the hoax call where presenters claimed to be the Queen. Nurse Jacintha Saldanha, found dead near the hospital on Friday, answered the call.

"Then to discover that, not only had this happened, but that the call had been pre-recorded and the decision to transmit approved by your station's management, was truly appalling," Lord Glenarthur said to Australia's Southern Cross Austereo Chairman Max Moore-Wilton.

A photograph of Ms Saldanha, a married mother-of-two, was released by Scotland Yard on Saturday. Police are treating her death as unexplained but not suspicious.

The Australian broadcaster is standing by the DJs who made the prank call. The company's CEO Rhy Holleran extended his sympathy but insisted no laws had been broken. In response, Lord Glenarthur said the DJs' actions and the radio station management's decision to broadcast the call was "appalling" and should never be repeated.

History of pranks

The station has been disciplined previously for shock jock pranks that have backfired.

"The immediate consequence of these premeditated and ill-considered actions was the humiliation of two dedicated and caring nurses who were simply doing their job tending to their patients," said Lord Glenarthur.

"The longer term consequence has been reported around the world and is, frankly, tragic beyond words. I appreciate that you cannot undo the damage which has been done but I would urge you to take steps to ensure that such an incident could never be repeated," he warned.

Mr Holleran said both presenters were "deeply shocked". But, he added, he was confident his DJs acted lawfully when they called the hospital at 5.30am in London.

Kate Middleton was admitted to the King Edward VII with severe morning sickness and released several days later. Mr Saldanha answered the hoax call and transferred it to another nurse who gave the station an update on the medical condition of the Duchess of Cambridge.

'Tragic but not foreseen'

"This is a tragic event that could not have been reasonably foreseen and we're deeply saddened by it," Mr Holleran said at a press conference in Australia on Saturday. "I spoke to both presenters early this morning and it's fair to say they're completely shattered."

The Australian Communications and Media Authority (Acma)has received complaints about the broadcaster following the airing of the prank and has disciplined the station in the past, including pranks involving the disabled and disadvantaged and one incident involving a 14-year-old girl who was strapped to a lie detector test and asked to discuss her sexual experiences.

"The Acma does not propose to make any comments at this stage, but will be engaging with the licensee, Today FM Sydney, around the facts and issues surrounding the prank call," he said.

The DJs from 2Day FM Mel Greig and Michael Christian, who will not return to work for the immediate future, were said to be "completely shattered" by the death of Ms Saldanha, 46 (pictured right). The Australia station has suspended adverts, and the show has been temporarily taken off-air.

"Prank calls as a craft in radio have been going for decades and decades, they are not just part of one radio station, or one network or one country, they are done worldwide," Mr Holleran said today.

Advertising suspended

The network has reportedly suspended all advertising on 2Day FM until Monday along with the show. While Mr Holleran did not think any laws had been broken, the chief executive of the London hospital John Lofthouse said his legal advice indicated the Australian broadcaster may have acted unlawfully.

Ms Saldanha, a duty nurse at the London hospital, answered the phone as there was no receptionist on duty in the early hours of the morning.

Family in mourning

Ms Saldanha's family said they were "deeply saddened by the loss of our beloved Jacintha" in a statement requesting privacy.

St. James's Palace said the duke and duchess were "deeply saddened" by the death. The hospital paid tribute to Ms Saldanha, who had worked for them for four years, calling her "a first-class nurse who cared diligently for hundreds of patients".