The Portuguese detective leading the investigation into the disappearance of Madeleine McCann today accused British police of helping her parents' defence rather than assist their attempts to find the truth.

Chief Inspector Goncalo Amaral claimed that British officers where following up leads provided by Kate and Gerry McCann rather than regarding them as suspects in killing their daughter.

The extraordinary attack follows two weeks of new claims which have cast doubt on the Portuguese police's suspicion that Mrs McCann accidentally killed Madeleine at the family's holiday flat in the Algarve on May 3.

Mr Amaral, the director of the Policia Judiciaria in Portimao, said: “British police have only worked on what the McCann couple want them to work on.

“They have only investigated tips and information developed and worked on for the McCanns, forgetting that the couple are suspects in the death of their daughter Madeleine.”

Portuguese police are convinced that the McCanns are responsible for Madeleine's death and the disposal of her body and that they are desperately trying to cover-up the crime by attempting to claim that she had been abducted. But a judge in Portugal has refused to order the couple to return for questioning due to lack of evidence.

The timing of the criticism will concern Portuguese prosecutors who are formally preparing to ask for British detectives to reinterview the McCanns. They want the couple to be asked 40 questions which they refused to answer before being made official suspects last month.

Mr Amaral, 47, was particularly critical of reports that British police were taking seriously an e-mail sent to official website of the Prince of Wales last week. The tip-off claimed that Madeleine had been abducted by a maid in revenge for being sacked from the Ocean Club complex where the McCanns were staying.

Mr Amaral told the Diario de Noticias newspaper that the lead “has no credibility for the Portuguese police”.

He added: “This story about abduction for revenge is another lead being worked on for the McCanns.

“The Ocean Club is in Praia da Luz, not London, which means everything said by employees, current or former, has already been investigated by the Policia Judiciaria. No e-mail, above all an anonymous one, which is easy to discover where it was sent, is going to distract our line of investigation.”

An un-named senior police source said: “After the war with the British media, we now have another with the English police.”

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