Praia da Luz: The parents of Madeleine McCann have said that the "guilt would never leave them" for not being there when she was abducted.

In an emotional first full interview, Gerry and Kate McCann said they had suffered every parents' worst nightmare and had been plunged into the "deepest, darkest despair".

The couple told how they had made arrangements with other families to check regularly on their children on the night of May 3 while dining a short distance away from their Algarve holiday apartment.

Gerry compared eating in the tapas bar at the Ocean Club Resort in Praia da Luz as like "having dinner in your garden".

But he said: "I think it's fair to say the guilt that we feel having not been there at that moment, irrespective of whether we had been in the next bedroom or not, will never leave us."

Speaking three weeks after Madeleine disappeared, Gerry added: "It was absolutely terrifying and when you go back to it, it still is."

First appeal

They spoke as Portuguese police made a dramatic first appeal to say they were looking for a white male suspect, aged 35-40, who was seen carrying a child in Praia da Luz at 9.30pm local time on May 3.

Police had been given the description by a British witness within 24 hours of the kidnap. The McCanns and British officials were told of it early in the investigation and they had been lobbying hard for police to release an appeal.

In their interview, Madeleine's parents admitted they were surprised by the limited information that officers were prepared to release under Portuguese law.

Gerry said: "Not knowing anything takes you back to the darkest places that really you don't want to go. I think in that period the worst feeling was helplessness."

The couple said they had been hurt by criticism for leaving Madeleine alone. The chances of her being abducted in Praia da Luz - where they were two days from the end of an "idyllic" holiday - were more than "100 million to one", they said.

Kate said: "At worst we were naive."

The couple feel strengthened by thousands of messages of support and said that "one evil act" has brought out the best in humanity and goodwill.

Details emerged on Friday night - separate to the interview - of the events before the abduction.

A source revealed that the McCanns had left their apartment unlocked while they dined with friends 40 yards away.

Regular checks

The children were checked at regular intervals by members of the group, the last time being at 9.10pm. Kate discovered Madeleine was missing at 10pm and found the front window shutters were wide open.

Asked about their emotions at that moment, Kate remained silent. But Gerry said: "There was the darkest, deepest despair."

Gerry , 38, a consultant cardiologist, added: "We have been reassured by the thousands of messages from people who have either done exactly the same or said they would have done the same. But I think it is fair to say the guilt we feel having not been there at that moment will never leave us."