Hundreds of reports from psychics and clairvoyants claiming to know the location of Madeleine McCann are being checked by Portuguese police following her disappearance four weeks ago today.

Detectives believe the abductor may try to alert them to the whereabouts of the four-year-old girl by claiming to have seen her in a dream or vision.

The Policia Judiciara (PJ) has two dossiers, 8cm thick, of apparent visions and sightings of Madeleine after she was stolen from the bed of an Algarve holiday apartment 28 days ago. The sightings have placed Madeleine at various locations across the world. Several addresses have been raided in the UK in the hunt for Madeleine.

Chief inspector Olegario Sousa said each clairvoyant claim was being taken seriously as one could contain a message from Madeleine's abductor.

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“That is one of the reasons that we cannot discard anything," he said. “We can’t put these messages in the bin. We must check them all in case it might be from the kidnapper.

"But the problem is the same, if there are indications which are enough to follow then we will go. If there isn't, we cannot do anything.”

The decision to treat such reports seriously will fuel criticism of the police investigation which has failed to find any trace of Madeleine to collect enough evidence to arrest any potential suspects. The method will draw comparisons with the Hollywood movie “The Gift” which featured Cate Blanchett as a psychic who uses her powers to track down a missing woman.

Mr Sousa said some the descriptions received by police in Portugal and Britain were as vague as dreams about a man in a house with trees and a road.

“Some of the information is about precise location or co-ordinates and that allows us to go to the place and we will check it,” he said. “Just a few days ago we got one address near Lagos [about five miles from Praia da Luz] but it didn't amount to anything.”

Mr Sousa said he did not believe they had heard from Madeleine's abductor: “If it was a message from the kidnapper, it will offer enough clues to help us to go to the right place.”

He said it was not unusual to investigate the claims of clairvoyants but added it was only one line of investigation.

“In this case the amount of information we have received is huge," he said. “Any information that comes to us, if there is enough to follow, we will check.”

It is not known if a “vision” was the source of the information which led to Portuguese detectives asking British police to raid a London home where they believed Madeleine might have been kept.

Debbie Seepersad from South Norwood was collecting her daughter Maressa, 12, from school when the police officers arrived on Wednesday last week.

“They said that because no-one answered the door when they knocked, they called through to their superiors and were told to gain entrance to the house,” said Ms Seepersad.

“I can understand why they did it. If it were my daughter I'd want them to knock on everyone's door. What irritates me is that they're not revealing their sources. Anyone could call up the police and give them anyone's address.”

A spokeswoman for Leicester Police, which is coordinating the investigation in Britain, said that a number of properties have been searched at the request of the Portuguese authorities but added: "We can't comment a great deal on the investigation and the particular leads because it's not our investigation. It's being led by the Portuguese police."

Madeleine's parents, Kate and Gerry, will tonight travel to Madrid ahead of meetings with politicians and charities involved with child welfare planned for tomorrow to raise the profile of the search for their daughter.

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