Portuguese police investigating the disappearance of Madeleine McCann will arrive in Britain this week to interview friends of the missing girl’s family, Portugal’s national police director has revealed.

Detectives and a public prosecutor will oversee interviews with at least four of the seven friends who had travelled to Praia da Luz with the McCann family when Madeleine was reported missing on May 3.

The most important witnesses are Russell O’Brien and his partner, Jane Tanner, who were dining with Madeleine’s parents, Kate and Gerry McCann, at the Ocean Club on the evening that she disappeared.

Mr O’Brien, a hospital consultant from Exeter, was away from the table for about 30 minutes at around the time that Mr and Mrs McCann claim that their daughter was abducted. Ms Tanner claimed that she saw a man carrying a child away from the McCanns’ apartment.

Detectives are also thought to want to interview Matthew Oldfield, who had checked on the McCanns’ apartment 30 minutes before Madeleine was reported missing, and his wife, Rachael. It is unclear if the Portuguese detectives will be present for the interviews or if they will be carried out by British officers.

AlÍpio Ribeiro, national director of the PolÍcia Judiciária, confirmed yesterday that the investigation would move to Britain as further criticisms of the operation emerged. “In a few days they will be travelling with a police team and the prosecutor of Portimão.”

Mr Ribeiro said police believed that Madeleine had died on May 3 and was not being held alive by an abductor.

“There is a scenario that has gained strength and has a greater degree of certainty,” he told the Spanish newspaper El Païs. “But we do not rule out any scenario.”

He insisted that officers had not initially suspected Mr and Mrs McCann but had made them official suspects only after a British sniffer dog suggested that a corpse had been in their holiday apartment and in a car they hired 25 days after Madeleine disappeared.

“It is true that in the first phase of the investigation we worked in the kidnapping scenario almost exclusively,” he said. “The British were the ones who did propose to us the use of the British cadaver dogs. Despite the fact that they do not give investigators hard proof, they made possible that we start exploring a new line of investigation.”

However, Mr Ribeiro said that a new team of officers had now started a full review of the investigation after Chief Inspector Gonçalo Amaral, the previous head, was demoted for criticising the British police for being too close to Madeleine’s parents.

“We are going to start a new phase in the investigation and we will review what we already have, not to criticise or judge what has been done but to try to decipher signals and events we might have not deciphered at the time when they did happen,” he said.

The new team is reported to have criticised the previous operation, claiming that they have spent the past fortnight processing information left lying around the police headquarters in Portimão on scraps of paper and following up leads ignored by the earlier team. A Portuguese police source told Expresso newspaper: “There was important material lying all over the place that hadn’t been considered by investigators. A lot of key information was discarded. The whole process is being reviewed. Putting the papers in order has been a massive task.”

It was also claimed that crucial evidence that could lead police to an abductor was contaminated by ash from policemen’s cigarettes. The ash was allegedly discovered by Portuguese forensic science experts among samples taken from the McCanns’ apartment soon after Madeleine vanished. Tests later showed that it was from cigarettes smoked by officers who had been in the apartment.

Lord Stevens of Kirkwhelpington, the former Commissioner of the Metropolitan Police, said yesterday that Mr and Mrs McCann, from Rothley, Leicestershire, were the victims of a witch-hunt. Writing in the News of the World, he said: “There’s absolutely no chance that the parents of Madeleine McCann would be charged with her murder in this country. It would be an outrageous miscarriage of justice if they were.”

He added: “I’ve been a detective at the most senior level for 30 years and have never seen such a witch-hunt, or one based on such flimsy evidence.”

Mr McCann, 39, a consultant cardiologist at Glenfield Hospital in Leicester, hopes to return to work before Christmas. He had planned to return this month but delayed the move after being made an official suspect on September 7. Mrs McCann, also 39, who worked as a part-time GP in Melton, has previously said she was unable to contemplate working again while Madeleine remained missing.

Times Recommends

• Air crash: ‘Everything is burnt. It is the closest thing to Hell’
• The true story of a passionate Korean 'spy'
• I shot Lennon in the back, Chapman tells parole board