The News of the World "jeopardised" a police inquiry into a spate of murders in Ipswich, a former senior police officer has alleged.
David Harrison, who worked on the inquiry into the killing of five prostitutes in Ipswich while at for the Serious Organised Crime Agency, told the Leveson inquiry into press ethics that the tabloid had hired ex-special forces soldiers to carry out their own surveillance on a suspect, which could have "seriously hindered" the police inquiry.
"I believe that by its actions NotW jeopardised the murder inquiry," the retired officer said in a witness statement.
Acording to Harrison the paper had their own team following the police's main suspect, who was later cleared of any involvement in the killings.
"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," he told the inquiry into media standards.
In his witness statement he said the surveillance team employed by the News of the World were supposed to "identify any suspects we were working on, and to identify 'us' and our operating base."
The former officer said the Daily Mirror also had a surveillance team who interviewed the first suspect.
Serial killer Steve Wright was convicted for the murders of five women in 2008.