Ex-Special Forces soldiers were employed by the News of the World to carry out surveillance on suspects and spy on a police intelligence unit during the hunt for the “Suffolk strangler”, the Leveson Inquiry was told today.

David Harrison, a retired investigator and intelligence officer with the Serious Organised Crime Agency (SOCA), said the operation mounted by the Murdoch-owned Sunday tabloid “jeopardised the murder inquiry” in 2006.

The bodies of five murdered women were discovered in and around Ipswich.

SOCA was brought into ‘Operation Sumac’ which eventually numbered 300 police officers.

The killer of the women, who worked as prostitutes in Ipswich, was branded the “Suffolk strangler” after two victims were found naked and asphyxiated.

Mr Harrison was part of the covert surveillance team observing potential suspects in a murder hunt that the media at the time were comparing to the hunt for the Yorkshire Ripper, Peter Sutcliffe.

The former SOCA officer told the inquiry “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.”

Asked how the now-closed newspaper may have learned SOCA were operating in Ipswich as part of the murder hunt, Mr Harrison said “It would have come from someone close to the investigation team, either the Suffolk inquiry or SOCA.”

The ex-officer’s written witness statement described an operational briefing by the SOCA branch commander, Simon Jennings, which identified a surveillance team “made up of ex-special forces soldiers” who had been given the job of identifying suspects already being observed, and to “identify ‘us’ and our operating base” in Suffolk.

Mr Harrison said the NOTW’s special team had “good knowledge of surveillance techniques” and that the SOCA officers had been followed on at least two occasions. Their cover was blown because  Mr Harrison said “they were sat in the position that we would have sat in if were doing the same job”.

In his witness statement to the Leveson Inquiry the former SOCA officer said the murder investigation -  which eventually led to the arrest and conviction of a local forklift driver, Steven Wright, for all five murders -  had been jeopardised buy the actions of the NOTW.

The former investigator said murderers revisited the scene of their crime, adding: “If that act is evidenced by a covert surveillance team, its value to the prosecution is extremely important.”

He said that if Wright had tried to revisit the scene or dispose of additional evidence, or to move a body that had not yet been found and realised he was being followed, he might have cancelled his plans. The statement continued : “He would not care whether he was being followed by a ‘legitimate’ surveillance team, or one employed by a newspaper. The evidence would have been lost and the prosecution weakened.”

Further damage to the extensive murder hunt could also have been caused, said Mr Harrison, because the police were dealing with a “private surveillance team getting in the way.”

The NOTW’s deployment of ex-special forces soldiers into a high-profile murder hunt was on the eve of the January 2007 trial of Glenn Mulcaire and Clive Goodman,  the private investigator and royal correspondent who were both convicted of illegal phone hacking.

 For News International, awaiting the imminent publication of a Commons investigation into the illegal activities of the NOTW, the timing of these new revelations could not be worse. They suggest nothing was off-limits in the tabloid’s efforts to get stories, with new questions expected to be asked about who authorised and paid the ex-soldiers and where else they may have been deployed.

The inquiry also learned from Mr Harrison that the Sunday Mirror used counter-surveillance techniques during the Ipswich murder hunt to secure an interview with a suspect. His witness statement said SOCA colleagues watched the suspect “being picked up and driven round by a team that carried out anti-surveillance maneuvers [sic] before dropping him off at an hotel to be interviewed.”