The Portuguese police inquiry into the disappearance of Madeleine McCann was condemned in the strongest terms by the country's public prosecutors, new documents revealed today.

Detectives were criticised for establishing "no element of proof " about what happened to Madeleine or even whether she was alive or dead.

Public prosecutors in Portimao overseeing the case said that none of the reasons her parents Gerry and Kate McCann were made official suspects, or "arguidos", were ever "confirmed or consolidated".

Detectives were even compared unfavourably with fictional sleuths Sherlock Holmes and Hercule Poirot as they were lambasted for achieving "very little in terms of conclusive results".

Police tactics were revealed in a 20,000-page "Madeleine File", detailing all aspects of the 14-month investigation made public yesterday.

Madeleine, three, vanished from her family's holiday apartment at Praia da Luz on 3 May last year. The police file included pictures of the room and Madeleine's bed. Her parents are now likely to take legal action against police in the country.

The case was initially led by top investigator Goncalo Amaral, who last month published a book on the investigation entitled Maddie The Truth about the Lie.

The huge police dossier contained a report by public prosecutors Joao Melchior Gomes and Jose de Magalhaes e Menezes about why the couple were not charged with any offence.

The report refers to the "objective circumstances" which justify the " non-involvement of the parents of Madeleine in any relevant criminal act".

It said they were not in the apartment when Madeleine disappeared and noted their "normal behaviour adopted before the disappearance and afterwards".

It said that "in reality, none of the indications which led to them being made arguidos came to be confirmed or consolidated later".

"No element of proof whatsoever was found which allows us to form any lucid, sensible, serious and honest conclusion about the circumstances" of Madeleine's disappearance from the apartment ... including, and most dramatically, establishing whether she is alive or dead, which seems more probable."

It continued: "The investigators are well aware that their work is not exempt from imperfections.

"They worked with an enormous margin of error and they achieved very little in terms of conclusive results, especially with regards to the fate of the unfortunate child. This is not, unfortunately, a police story, a crime fit for the investigative mind of a Sherlock Holmes or a Hercule Poirot, guided by the illusion that the forces of law and justice always restore order."

The report also revealed why the McCanns were not charged with " abandonment" of their children on the night Madeleine vanished. It said the couple did not knowingly leave their children in any danger and had been "keeping an eye on them".

It continued: "While it is a fact that Madeleine disappeared from the Ocean Club apartment, the circumstances and manner of how this happened is not known.It is obvious that neither of the defendants, Gerald or Kate, acted with intent ... they could not predict that the resort they had chosen to spend a few days' holiday would leave the lives of any of their children in danger.

"It was located in a quiet place, where the majority of residents are foreign citizens of the same nationality and without any known history of this type of crime.

"Although they left their daughter alone with her siblings in the apartment, sometimes for extended periods, it's true that, in any case, they were keeping an eye on them. We must also recognise that the parents are already paying a heavy penalty - the disappearance of Madeleine - for their carelessness in monitoring and protecting their children."

The prosecutors also rejected the theory that the couple had been involved in disposing of their daughter's body saying: "It would be always left to explain how, where, when, with what means, with whose help, in a restricted space and time."

A source close to the McCanns' legal team said action against the Portuguese police was now increasingly likely. He said: "Given this blatant misrepresentation of evidence, legal action against the Portuguese police is very much on the agenda.

"The lawyers are considering very seriously whether action needs to be taken against individual officers when evidence was clearly misrepresented in such obvious ways at such crucial times."

The couple's official spokesman Clarence Mitchell said the priority was still the search for Madeleine but admitted legal action against the police was an option.