Kate and Gerry McCann became concerned about the work of Portuguese police

UP to eight “very important” leads in the hunt for Madeleine McCann have been handed to Scotland Yard by a leading firm of private detectives, it emerged yesterday.

In a second confidential visit to Spain in three weeks, officers from the Yard’s McCann squad held detailed discussions with the Barcelona-based investigators of the firm Metodo 3.

The four-strong British police team later took possession of its entire dossier packed into 30 boxes of documents.

Francisco Marco, the agency’s director, said yesterday he was convinced there were “six, seven or eight very important leads” in the files handed to Scotland Yard.

He insisted every new piece of important information had been previously passed to the Portuguese police but claimed it was ignored.

Speaking on Spanish television yesterday, Mr Marco said: “Every time anyone from Metodo 3 went to Portugal they were continually followed and monitored to see what they were doing.

“We were never allowed to do a proper job. Scotland Yard can now continue with all the work we did outside of Portugal and inside Portugal as well.

“The English police are now continuing with an investigation which should never have been closed.”

Mr Marco believes the material handed to the Yard team on Tuesday could shed fresh light on Madeleine’s fate.

He added: “We have provided them with all the documents and information we have collated worldwide about Madeleine’s disappearance so they can continue the investigations we carried out in Spain, Morocco and the rest of the world.”

The Yard is conducting a step-by-step review of the hunt for Madeleine who was aged just three when she vanished from a flat in the holiday resort of Praia da Luz on the Portuguese Algarve coast in May, 2007. Metodo 3 were hired by Madeleine’s distraught parents, Kate and Gerry McCann, in September that year when they became concerned about the quality of the Portuguese investigation

Last night the McCann’s spokesman Clarence Mitchell said the family were “pleased” detectives are working on the case.

But Mr Mitchell added: “Kate and Gerry will simply not be commenting whilst the Metropolitan Police review of Madeleine’s case is under way.”

The Yard has assigned 30 detectives to the review of the McCann case.

Codenamed Operation Grange, it was launched in May this year after the McCanns appealed to Prime Minister David Cameron.

So far, members of the Grange squad are understood to have made three trips to Portugal and two to Spain.

During the latest visit, it is believed the Yard team discussed the possibility that Madeleine was smuggled out of Portugal to Morocco.

Mr Marco believes it is “very possible” the little girl was taken to North Africa and has made extensive inquiries but without success.

Metodo 3 was reportedly paid £50,000 a month to search for Madeleine. Mr Marco was in daily contact with doctors Kate and Gerry, from Rothley, Leics, and at one stage had 40 staff working on the case.

But in December, 2007, he faced criticism after claiming in a newspaper interview that he knew who had abducted Madeleine and would have her home for Christmas.

Scotland Yard refused to comment on the latest visit to Spain.