Retired police officer said he was personally followed by News of the World surveillance team

Lisa O'Carroll, guardian.co.uk

The News of the World "jeopardised" the hunt for the Ipswich serial killer in 2006 after it hired former special forces soldiers to follow a police surveillance team tracking suspects, the Leveson inquiry has heard.

Dave Harrison, a retired officer with the Serious Organised Crime Agency (Soca), was part of a surveillance team set up to keep tabs on suspects in the high-profile murder hunt.

Harrison told the Leveson inquiry on Monday that he was personally followed by the Sunday tabloid's team, which appeared to have professional knowledge of surveillance techniques.

"I believe that by its actions, News of the World jeopardised the murder inquiry," he said.

"If our surveillance had been weakened by having to try and avoid other surveillance teams looking for us, if we had lost the subject, he may have gone and committed further murders because we were dealing with something else."

In December 2006, Suffolk police asked Soca to provide surveillance officers to follow suspects in the then-unsolved murders of five women working as prostitutes in Ipswich, the hearing was told.

Harrison said he and his colleagues were told at a briefing that the News of the World had employed its own surveillance team to identify who they were, where they were based and who the suspects were.

Asked how the paper learned that Soca officers were being sent to Ipswich, he said: "My opinion is it would have come from someone close to the investigation team, either the Suffolk inquiry or Soca."

He said that, on at least two occasions, a vehicle parked up on a roundabout on the outskirts of the town attempted to follow the Soca surveillance team.

"We identified them because they were sat in the position that we would sit in if we were doing the same job," he added.

"We were told that they were probably ex-special forces soldiers who would have a good knowledge of surveillance techniques."

In his written witness statement submitted to the Leveson inquiry, Harrison said the paper jeopardised the inquiry in two ways.

"Firstly, many murderers revisit the scene of the crime. If that act is evidenced by a covert surveillance team, its value to the prosecution is extremely important. In this case, if the suspect had decided to revisit the scene, to dispose of additional evidence, or to move a body that had not yet been found and he realised he was being followed, he may have cancelled or postponed his trip.

"He would not care whether he was being followed by a 'legitimate' surveillance team or one employed by a newspaper. The evidence would be lost and the prosecution case weakened."

Harrison said the paper could also have compromised the police efforts to find the killer because it would have had to deal with a "private surveillance team getting in the way".

The Sunday Mirror used counter-surveillance techniques while driving one suspect in the Ipswich murders to a hotel for an interview, Harrison also told the press standards inquiry on Monday.

He said that during another briefing, he was advised that the Sunday Mirror surveillance team had picked up the first suspect for an interview.

"The surveillance team I was part of was not on duty at the time that the first suspect was interviewed by the Sunday Mirror. Colleagues on the surveillance team that was on duty advised us that they had watched him being picked up and driven round by a team that carried out anti-surveillance manoeuvres before dripping him off at an hotel to be interviewed," Harrison said in his written witness statement.

Steve Wright was handed a life sentence in February 2008 after being convicted of killing all five women.

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(Photo of the last edition of the News of the world by HowardLake via Flickr)