The father of Madeleine McCann has admitted the possibility that his missing daughter may be dead.

In the first interview with Kate and Gerry McCann since they were formally cleared of involvement in the case, Mr McCann says: "I will be honest. We have got no idea whether Madeleine is alive or not. What we are certain of is that there is absolutely no evidence."

It is believed to be the first time Mr McCann has publicly spoken of the possibility that Madeleine may be dead.

The comments can be seen in a short video posted on the website of Portuguese newspaper Expresso, which conducted the interview.

The couple look relaxed in the clip, both wearing the yellow wristbands of the official Find Madeleine campaign.

In the interview, Mrs McCann strongly criticises the Portuguese detective who named her and her husband as suspects in their daughter's disappearance.

Mrs McCann lambasts the decision of Goncalo Amaral, the former head of the investigation, to make a series of allegations against the McCanns in a book which he wrote.

The Truth About the Lie was published in Portugal six weeks ago, days after Portuguese prosecutors announced on July 21 that they were shelving the case and lifting Mr and Mrs McCann's status as "arguidos", or official suspects, following Madeleine's mysterious disappearance from the family's Algarve holiday apartment.

The couple made a brief statement after being cleared but have not spoken out at length until now.

Although appearing to fear the worst, Mr McCann, originally from Glasgow, and his wife, both 40, who now live in Rothley, Leicestershire, speak of their hopes for finding their daughter and their fears of being arrested last summer.

Asked if the couple feared being arrested or accused by Portuguese police over their daughter's disappearance, Mr McCann said: "If you believe what was written in the papers, then of course we feared it. The situation for us was very frightening, of course it was."

Asked whether this was why they returned to the UK in September last year, Mrs McCann replied: "They could still have arrested us, couldn't they. They could have stopped us from going home."

Clarence Mitchell, the couple's official spokesman, said: "Kate and Gerry have chosen to speak out to an element of the Portuguese media now because they still firmly believe that there may well be important information that somebody knows in Portugal.

"It is important the message is targeted in that region initially, and Kate and Gerry will assess the reaction to their interview and public opinion in Portugal before deciding on whether to do any further media interviews in the near future.

"Everything Kate and Gerry are doing now is geared towards assisting their own investigation into finding Madeleine. They will do everything they can to generate vital new leads."

Meanwhile, a Portuguese police video showing British sniffer dogs reacting to the McCanns' hire car and in their holiday apartment was made public yesterday.

The two specialist animals - one capable of detecting corpses and the other trained to find human blood - carried out searches in the Algarve in early August last year.

Footage posted on a tabloid newspaper's website shows the cadaver dog, named Eddie, barking loudly next to the driver's door of the McCanns' Renault Scenic rental car.

It also shows the blood sniffer dog, called Keela, giving a "passive indication" behind the sofa in the apartment where Madeleine disappeared.

Madeleine was days away from her fourth birthday when she vanished from her family's holiday apartment in Praia da Luz on May 3 last year as her parents dined with friends nearby.

Despite a huge police investigation and massive coverage in the Portuguese and British media, she has never been found.