Former News of the World editor Andy Coulson was aware that hacked voicemail messages were the source of a story about former Home Secretary David Blunkett having an affair, a court has heard.

Neville Thurlbeck, a former chief reporter at the News of the World, said the story originated from the illegal interception of between 15 and 25 voicemails left by Mr Blunkett on the phone of the woman involved in 2004.

Mr Thurlbeck became aware of the messages when they were played to him by the paper's private investigator, Glenn Mulcaire, the High Court in Edinburgh heard.

The witness then told Coulson that the messages came from "Glenn, our private investigator", the jury heard.

Coulson, 47, the Prime Minister's former director of communications, is on trial accused of lying under oath in the 2010 perjury trial of former Socialist MSP Tommy Sheridan. He denies the charge.

Among the claims, prosecutors allege that Coulson falsely stated that, before the arrest of private investigator Glenn Mulcaire and News Of The World journalist Clive Goodman in 2006, he did not know that Goodman was involved in phone hacking with Mulcaire.

The court was today shown an exclusive front page News of the World story written by Mr Thurlbeck and printed on August 15 2004. It had the headline "Blunkett Affair with A Married Woman."

Mr Thurlbeck, 53, told the court that intercepted voicemail messages left for the woman in question by Mr Blunkett had played a part in the story.

He put the number of messages accessed at "approximately more than 15, less than 25".

The witness said he first heard the messages around the late spring or early summer of 2004.

"I was contacted by Glenn Mulcaire who played me the tape of an interception down the phone," he told the court.

He agreed with advocate depute Richard Goddard, prosecuting, that it "appeared to have the potential to be a very major news story".

He said he then "rang Andy Coulson", who was on holiday at the time, and told him that he had been played a "voicemail message left by David Blunkett".

"I said it was our private investigator," he told the court.

He said Coulson initially reacted with "extreme caution" over the story and told him to stop.

When Coulson got back from holiday, a meeting was later held to discuss the public interest justification for the story, the court heard.

Asked what he told Coulson about the source of the story, he said: "I said it was done by Glenn, our private investigator."

Mr Thurlbeck insisted he had not used the investigator's surname during the conversation.

Mr Goddard put it to the witness: "You told Mr Coulson that the hacked voicemails in relation to Mr Blunkett had come from the News of the World's private investigator Glenn?"

"That's correct," Mr Thurlbeck replied.