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."
See the interview on Calendar tonight at 6pm.
More top news
Samantha Baldwin, 42, and her sons Louis Madge, nine, and Dylan Madge, six, haven't been seen for two days.
Police want to speak to anyone who knows what Thomas Rhodes was doing the night before he was found
Alexander Palmer, of Selborne Street, was found guilty of six counts of indecent assault and two counts of gross indecency with a child.