Hoax callers from a radio station in Australia got information from the hospital treating the pregnant Duchess of Cambridge.
King Edward VII Hospital in London received a call from two presenters from Sydney radio station 2Day FM.
Presenters Mel Greig and Michael Christian posed as members of the Royal family - believed to be the Queen and Prince Charles - and were transferred to a nurse who gave them an update on Kate's condition. It was played out live on the radio show.
A spokesman for the hospital said: "This call was transferred through to a ward and a short conversation was held with one of the nursing staff. King Edward VII's Hospital deeply regrets this incident."
Reporters camped outside the hospital were Kate is being treated. Pic: PA
John Lofthouse, chief executive at King Edward VII's Hospital, added: "This was a foolish prank call that we all deplore."
Kate, who is expecting her first baby with Prince William, is being treated for hyperemesis gravidarum - extreme morning sickness.
A spokesman for the couple has not commented, and the hospital said telephone protocols are under review.