Now Portuguese police admit: 'There is no proof that Madeleine is dead'

A senior source close to the inquiry said: "We do not have proof the girl is dead. If we had that kind of evidence we would not be considering the theory she was abducted."

The admission amounts to a U-turn. For six months officers have been convinced Madeleine, who was three, died in an apartment in Praia da Luz and her parents disposed of the body using a hire car rented 25 days after she vanished.

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But following a meeting with the Forensic Science Service last week, Portuguese detectives have conceded they have no proof to support the theory.

"We are no longer sure that she is dead," a source told Daily Mail sister paper Evening Standard.

The revelation comes as police prepare to reinterview Kate and Gerry McCann, who remain official suspects over their daughter's disappearance from the Mark Warner Ocean Club resort on 3 May.

Friends of the couple who were with them at a tapas bar when she vanished will also be questioned.

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Letters requesting the interviews take place in Britain were sent today from Portugal.

The request included a list of questions to be put to the McCanns and their friends.

It now appears much more likely that the parents could have their official suspect — or arguido — status removed, instead of them being charged. Clarence Mitchell, the McCanns' spokesman, said: "The thrust of the inquiry for the last six or seven months has been wrong.

"If the police now believe that abduction is the strongest possibility ... that is very encouraging.

"Madeleine did not die in the apartment. The police should be focusing on who took her, and finding her.

"They must also accept Kate and Gerry should be eliminated from the inquiry."

The McCanns, who deny involvement in their daughter's disappearance, were made suspects after analysis of evidence from the apartment and hire car, which was sent to the Forensic Science Service in Birmingham.

While no official comment has ever been made on the findings, police in Portugal had briefed previously that it showed Madeleine died in the apartment.

They leaked evidence including the discovery of Madeleine's hair and bodily fluids in the boot of the hire car.

Tests on the car by the McCanns' own team showed no DNA link to the girl.

The detective who originally led the inquiry, Gonçalo Amaral, was sacked for briefing against the McCanns.

He was replaced by Paulo Rebelo, and in recent weeks police have indicated a greater willingness to look at other theories.

Today the couple, both doctors from Rothley in Leicestershire, made a new appeal for anybody at the resort when Madeleine vanished to contact police.