When approached by Calendar, a spokesman said: "North Yorkshire Police invited the National Policing Improvement Agency to conduct a second voluntary review of the investigation in 2010.
"Their report concluded that the investigation had been conducted with integrity and objectivity and that, where individuals had been subject to investigation, no investigative opportunities had been overlooked.
"The reviewers noted that good practice was evident in the investigation and that those strategies reviewed conformed to nationally approved standards."
As the inquiry into Claudia's disappearance enters its fifth year, they have called for a new inquiry with a wider remit. But, they say even that may be too late and whoever is responsible for Claudia's disappearance may have got away with it.
"I just feel anger that four years on there's someone sat there somewhere, probably seeing the publicity, seeing the pain the family's going through and ..they've got away with it. With abducting her or whatever it is. And I just think how can they live with themselves?"
"The time, statistically, they said its very unlikely that a stranger was involved in this, and that was dismissed. I just feel that any sightings, or any pieces of information that are linked to someone who didn't know her should not be dismissed. They should be taken on board."