Kate Middleton was hacked 155 times by a reporter on the News of the World who said he snooped on her voicemails on Christmas Eve and Christmas Day, the Old Bailey has heard.

Clive Goodman, the paper's former royal editor, also revealed for the first time he directly hacked the phone of Prince William, adding that police had failed to ask him a single question about it in the eight years since he was arrested on related charges.

He told jurors he hacked Prince William 35 times, Prince Harry nine times and the Duchess of Cambridge 155 times.

Goodman said he had not been asked about this by the police or any other authority when he was arrested on related charges in 2006 or any time since.

"I've never been asked before. The Metropolitan police, Crown Prosecution Service did not ask me these questions in 2006 and 2007. I've never been asked by any inquiry any time about this," he said.

He first hacked Middleton on 21 December 2005, the jury heard, and continued to hack her on Christmas Eve, Christmas Day and Boxing Day. His first hack of Prince William was revealed to have taken place at the end of January 2006.

Goodman told jurors: "I'm really not the slightest bit proud of this. I don't want anyone to think I'm not ashamed."

He also hacked the phone of Kate Waddington, the personal assistant to Sarah Ferguson, the Duchess of York, 160 times.

Goodman also said of Glenn Mulcaire, who was also arrested in 2006 for hacking members of the royal household: "Virtually every story in the paper was ground through the Glenn Mulcaire mill."

Under cross-examination by Timothy Langdale QC, who is acting for the paper's former editor Andy Coulson, Goodman told the jury that he was not on trial for hacking and the prosecution had told him he faced no further charges on this offence.

Turning to Langdale, he said: "Now that you are asking them [the questions], I'm quite happy to get them out there and get everything in the open."

He said he was being as "honest and open" as he could be on the subject. "My entire life has been exposed. I've never been asked these questions ... Anyone who wants to ask me questions, they will get straight answers as indeed you are getting today."

He told jurors that Middleton, who was dating Prince William, back in 2005 was a "figure of increasing importance around the royal family. There were discussions of her and Prince William marrying, moving in, settling down. She had started receiving royal status around the royal family."

Langdale put it to him that "one of the things you must have been worried about more than anything else in 2006" was that it would be discovered he was hacking Princes William and Harry and Kate Middleton.

He denied this and said his biggest fear was that he would have to carry the can for all the activities of Mulcaire who was arrested and jailed along with Goodman in January 2007 for hacking-related offences.

"I was terrified of the whole thing. I was more frightened of being blamed for Glenn Mulcaire's hacking," he said.

Jurors have previously heard that Kate Middleton and Prince Harry had been hacked. They have also seen emails relating to alleged hacks of Prince William when he was at Sandhurst in 2006, but Goodman's evidence on Wednesday is the first time it has been admitted.

The Duke and Duchess of Cambridge have known each other since 2001 when they met at St Andrew's University and were exposed by the newspapers as a couple in 2004.

The trial has already heard that personal messages left by Prince William for Kate Middleton in 2006 in which he called her "babykins" were hacked by the News of the World.

Goodman was jailed in 2005 after admitting being involved in the hacking of three royal aides, Prince Charles's communication secretary Paddy Harverson, the prince's aide, Helen Asprey, and Jamie Lowther-Pinkerton, private secretary to Princes William and Harry.

He was back in the witness box after an eight-week absence due to illness to finish his evidence.

Because of the long lapse of time between the first part of his cross-examination, the judge opened proceedings by refreshing the jury's memory as to Goodman's previous evidence.

Jurors were reminded that Goodman had claimed that Coulson had told him to tell police he was acting as a "lone wolf" and that he had gone "off the reservation" when asked about his activities in 2006.

Coulson has been charged with one hacking conspiracy, a charge he denies.

The trial continues.