A former News of the World journalist has told a court that Andy Coulson was aware that voicemail messages on the phone of murdered teenager Milly Dowler had been intercepted.

Neville Thurlbeck, the tabloid's one-time chief reporter, also said that hacked messages were the source of a story about former Home Secretary David Blunkett having an affair.

Coulson, 47, the Prime Minister's former director of communications, is on trial at the High Court in Edinburgh accused of lying under oath in the 2010 perjury trial of former Socialist MSP Tommy Sheridan.

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 Mr Goodman was involved in phone hacking with Mr Mulcaire. He denies the charges.

Jurors were shown a copy of a story about the missing schoolgirl that appeared in an edition of the paper on April 14, 2002, with the headline "Milly Hoax Riddle Messages on Mobile Probed".

The story, which appeared at a point when Milly had been missing for more than three weeks, contained precise timings and words that appeared to have been left on her phone.

Mr Thurlbeck told the court that he was looking after the newsdesk that week in the absence of Greg Miskiw, while Coulson, as deputy editor at the time, was filling in for editor Rebekah Brooks, then Wade.

He said the schoolgirl's disappearance was "right at the top of the news agenda" and Coulson had said he wanted to make sure that the paper "was all over this story".

Mr Thurlbeck said he had instructed Mr Mulcaire to get involved with the paper's investigation into the Milly Dowler case and to research all possible suspects, including members of the family.

He was shown a note taken from Mulcaire's house in 2006 which had the journalist's name at the top, as well as the date April 10, 2002 and the names and telephone numbers of Milly's parents.

The witness said Coulson was "not initially" aware that the private investigator had been tasked with working on the story.

Advocate depute Richard Goddard, prosecuting, asked: "When did he become aware you had instructed Glenn Mulcaire?"

Mr Thurlbeck responded: "When Glenn came back with voicemails".

He added: "He came back with a tip off. A voicemail which had been intercepted on her phone."

Mr Goddard asked: "Did Mr Coulson tell you to take this recording straight to the police to help their inquiry?"

Mr Thurlbeck said: "The short answer is no. Mulcaire said to me that the recording had been intercepted by his police contact.

"He said he was getting this information from an unofficial police contact which wouldn't be unusual from a good private detective.

"Therefore we believed for a very long time that the police were fully aware of this line of inquiry and therefore for us to go back to the police would be a pointless exercise as they already had it."

Asked what he had told Coulson when asked where the information had come from he added: "That there was a police source who was revealing to us via Glenn the existence of these voicemails and the content of them."

Pressed by the advocate depute, he added: "I didn't have to explain who Glenn was".

He said Coulson had seen transcripts of the voicemails, one of which suggested that Milly might have been working via a recruitment agency at a factory in the north.

The court heard the paper sent a team of about five reporters and photographers in the hope of discovering the schoolgirl at the business.

Asked why police had not been contacted, the witness said: "That was not my call. That would always be the editor's call".

"We were confident that the police had this because we were getting it from a police source". He said it seemed "beyond comprehension" that a team of murder detectives would have overlooked it.

Mr Goddard said: "You say the decision not to even try taking this to police was a decision ultimately made by Andy Coulson?"

"Yes," the witness replied.

He added: "He trusted the source because he trusted me."

Earlier the court heard that the story about Mr Blunkett's affair originated from the illegal interception of between 15 and 25 voicemails he left on the phone of the woman involved in 2004.

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

Mr Thurlbeck, 53, told the court 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 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.