The detective at the centre of the investigation into double murderer Christopher Halliwell has questioned why police failed to follow up his connection to other killings.
Steve Fulcher also said he had been hung out to dry in the wake of Halliwell's convictions last week.
Former detective superintendent Mr Fulcher caught Halliwell, 52, following the abduction of Sian O'Callaghan from outside a nightclub in Swindon in March 2011.
The taxi driver would go on to confess to murdering both Miss O'Callaghan and another woman, Becky Godden.
But now Mr Fulcher has linked Halliwell to further murders.
Mr Fulcher, now a security consultant in Somalia, said today there was "unquestionable" evidence that Halliwell killed again.
"I spent a lot of time with Christopher Halliwell.
Mr Fulcher said police investigating Halliwell were aware of missing chef Claudia Lawrence, as well as the case of Linda Razzell.
Miss Lawrence was last seen on March 18 2009 and was reported missing the following day after she failed to turn up for a shift at work at the University of York.
Mrs Razzell vanished after setting off to work at Swindon College in 2002. Her body has never been found.
Mrs Razzell's husband, Glynn, is currently serving a life sentence for her murder, but still claims he is innocent and the victim of a wide-ranging conspiracy.
Mr Fulcher said that Mrs Razzell had a "direct relationship" with Halliwell.
"My issue was no investigation has occurred. We were aware of Claudia Lawrence, we were aware particularly of Linda Razzell.
Father-of-three Halliwell, formerly of Nythe in Swindon, originally confessed the crime to Mr Fulcher after leading the detective to the field where he had dumped the body of Miss O'Callaghan.
But the confessions were later ruled inadmissible by a High Court judge because MrFulcher failed to caution the killer, breaching police procedural rules for the interviewing of suspects.
The detective was later found guilty of gross misconduct by a police disciplinary panel but kept his job after receiving a final written warning. He resigned from Wiltshire Police several months later, ending his 27-year police career.
Mr Fulcher said there was a flaw in the Police and Criminal Evidence Act, which prevented police officers from acting in the interests of victims.
He said in these cases there was a conflict between a victim's right to life, versus the accused's right to remain silent.
Mr Fulcher said this did not allow police officers to act in the interest of parties whose lives are threatened, which was particularly pertinent in live cases of terrorism and kidnap.
When asked whether he felt he had been hung out to dry, he said: "I have, obviously."