The former royal editor of the News of the World tabloid hacked the phones of Britain's Prince William, his wife Catherine and brother Prince Harry dozens of times, a trial heard.

Former royal editor Clive Goodman illegally listened to the voicemails of the then-Kate Middleton 155 times, William 35 times and Prince Harry nine times, the jury was told.

The trial over phone-hacking had already heard that Goodman had targeted the royal trio but it was the first time the full extent of the hacking had emerged.

Owner Rupert Murdoch shut down the Sunday tabloid in disgrace in 2011.

The details came out as Goodman was being cross-examined by Timothy Langdale, the lawyer of Andy Coulson, Goodman's editor at the time of the offences.

Goodman and private investigator Glenn Mulcaire were both convicted in 2006 and jailed for phone hacking but are now on trial for conspiring to commit misconduct in public office.

The journalist said police and prosecutors had not asked him about hacking William, Kate and Harry at the time in 2005 and 2006.

"I have been as open and honest about hacking as I can be but nobody has asked me any questions about this before," Goodman said.

The trial, which started last October and is expected to finish in June, has already heard that William referred to Kate as "babykins" in one message.

In another he put on a high-pitched voice and pretended to be his "ginger" brother Harry's then-girlfriend Chelsea Davy.

Among the seven defendants on trial are Coulson, who went on to work as media chief for Prime Minister David Cameron, and Rebekah Brooks, who rose to become the top executive in Murdoch's British newspaper unit.

Coulson is accused of phone hacking and paying public officials, while Brooks faces similar charges as well as one of hiding material from the police in the last days of the News of the World.