The police case against Kate and Gerry McCann suffered a severe setback last night when a Portuguese prosecutor said that no new evidence had been gathered to justify reinterviewing the couple.

Luis Bilro Verão, the lead public prosecutor, said that the police had failed to produce new evidence against the couple during the 13 days since they were made official suspects in the death of their daughter.

In his first official statement, he said that the McCanns remained arguidos, or official suspects, and that the investigation against them continued. He offered new hope to the McCanns by stating that all lines of inquiry were being investigated.

The admission comes as the McCanns said that they feared that they were being bugged as part of the investigation. They also believe that the scientific evidence against them is deeply flawed.

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Mr Verão said: “Since the police have not collected any elements of proof after the parents became arguidos on September 7 that justifies any new actions, I have not requested any new interviews.”

Last night’s statement follows a review of the evidence by Judge Pedro Daniel dos Anjos Frias, who had been asked to approve new interviews and searches requested by the PolÍcia Judiciária, the Portuguese equivalent of the CID. Detectives wanted to reinterview the couple after they refused to answer 40 key questions.

The Portuguese police case was so weak at the time the couple were made official suspects that they had to be released on the lowest form of bail and were allowed to return home to Rothley, Leicestershire, two days later.

Detectives hoped that samples taken from the couple’s hire car and holiday apartment would prove that Mr and Mrs McCann were responsible for accidentally killing their daughter while on holiday in Praia da Luz 140 days ago. However, Mr Verão has indicated that the evidence remains too weak to charge the couple with accidental homicide and hiding the corpse of their daughter. He could authorise further questioning if new evidence is found.

Clarence Mitchell, the McCanns’ spokesman, said: “This information has been conveyed to Kate and Gerry directly. It is now for their Portuguese lawyer to assess very carefully but, on the face of it, it does appear encouraging.”

Mr and Mrs McCann were convinced that their calls were tapped in Portugal because questions asked by detectives focused on private conversations with friends and family.

But the couple now believe that their calls are still being recorded as part of a surveillance operation.

“British police warned Kate and Gerry when they were in Portugal that their phones and e-mails might have been tapped into,” a source said last night. “Everyone involved is careful, particularly with their mobile phone calls and what they say. There was an assumption from the early days that mobile communications are unsafe and could be listened to.

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