Competition between British police forces hindered the investigation into the disappearance of Madeleine McCann and have had a long-term negative effect on the case, according to the author of an unpublished Home Office report.
Its author, Jim Gamble, the former head of the Child Exploitation and Online Protection Centre (Ceop), also told Sky News that so many agencies from the UK got involved with the investigation it damaged relations with Portuguese police.
Within weeks of the three-year-old going missing from Praia da Luz in May 2007, Ceop, the Metropolitan Police, the Serious Organised Crime Agency and the National Police Improvement Agency all intervened, creating "frustration" and "resentment" among Portuguese officers, his report found.
Mr Gamble, whose report was commissioned by former home secretary Alan Johnson in 2009, said the initial response to her disappearance was "haphazard" and that local police had failed to follow up potentially crucial information.
But he said Britain was warned not to try to behave as a "colonial power" after challenges to the approach to the investigation of the Portuguese police.
Mr Gamble told Sky News: "When this (the disappearance) happened your first gut reaction is that you want to help, a child has gone missing. In Ceop we were no different than anyone else.
"So there is this rush to help in the early stage and I think because the UK did not have a structure for dealing with this ... so everyone came with best intention, that created a sense of chaos and a sense of competition ... and in many instances in my opinion wanting to be seen to help.
He added: "I've no doubt relationships from the outset with the Portuguese were impacted by it and I think that had a long-term negative effect on the investigation.
His view was echoed by Anthony Summers, co-author of the forthcoming book Looking For Madeleine, who said: "It was a case of too many cooks, all well-intentioned, spoiling the broth of the initial investigation, and then the mistakes, or should I say mis-steps, began to pile one upon another."
Mr Gamble's report, which was delivered in 2010, also criticised the decision of the Association of Chief Police Officers to put Leicestershire Police in charge of the operation, saying it was a mistake as the force was ill-equipped for the size of the investigation, Sky News said.
Despite his criticisms of the initial Portuguese investigation, Mr Gamble said that a response by Britain to a similar situation would be no better as it has not followed up on one of his recommendations, the establishment of a national centre for missing children.
The Home Office, which declined to release the report under Freedom of Information laws, has not responded to requests for a comment.