Madeleine: Portuguese police accuse Home Secretary Jacqui Smith of stalling investigation

Portuguese police said the nine-month case had reached "a stalemate" because the Home Office had failed to respond to a list of demands sent almost a month ago.

Investigators sent a formal letter of appeal to Whitehall on January 7, asking that the seven friends who dined with Kate and Gerry McCann on the night of May 3 should face fresh police interrogations.

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Three weeks have passed and the Home Office has yet to make any response to the letter, the Portuguese newspaper Correio da Manha reported.

British police cannot carry out the interviews on behalf of their Portuguese counterparts until the request has been rubber-stamped by the Home Secretary.

And Portuguese police claim they cannot progress with their investigation until the interrogations are carried out.

A source said the latest delay had stalled the entire case, adding: "It is very strange that we have heard nothing.

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"There seems to be no sense of urgency on their part. But we cannot proceed until these interrogations have been carried out. It is a stalemate."

The police and the public prosecutor were notified three weeks ago that the letters had been delivered to the Home Office, the newspaper said.

Chief Insp Paulo Rebelo and his police team spent four months preparing the formal legal documents, which set out the requests for the so-called Tapas Seven to be re-interviewed and a list of questions for them to face.

The letter also listed a number of personal items the Portuguese police want seized from the McCanns, including Mrs McCann's diary, Mr McCann's personal laptop and possibly Madeleine's favourite Cuddle Cat toy.

Portuguese police want to be present when the Tapas Seven are questioned, and believe they have identified a series of contradictions and inconsistencies in their witness statements about the events of May 3.

They are expected to call for the McCanns to face another round of interviews after their friends have been re-interrogated.

The couple, who remain official suspects in the case, have said they are willing to be questioned again but have always insisted they were not involved in their daughter's disappearance.

A friend, who asked not to be named, said: "It's a bit rich that the Portuguese police are complaining about speed, almost nine months after Madeleine disappeared."

A Home Office spokesman refused to confirm if it had received the letters of appeal from the Portuguese police.

McCann family spokesman Clarence Mitchell said: "For some months now we have actively offered to assist this process, to get it underway as soon as possible.

"Kate and Gerry's friends are keen that it should happen soon and want any bureaucracy - whether it's in Portugal or England - to be cleared quickly.

"Any inconsistencies the police believe exist in their evidence can be cleared up very quickly and then we hope Kate and Gerry's names will be cleared.

"As far as we are concerned this cannot happen soon enough."