Formal suspects under Portuguese law receive more legal protection, including the right to remain silent during questioning and the right to legal representation.

Kate McCann faced a gruelling session yesterday at the headquarters of the Policia Judiciaria - Portugal's CID - in the city of Portimao. She eventually emerged at just before one o'clock this morning.

Her lawyer Carlos Pinto de Abreu read a brief statement to the waiting journalists.

He said: "Kate was held throughout the whole day as a witness and she remains a witness.

"It is obvious that investigations will continue, and I cannot say anything else because of the secrecy laws."

When it became clear that Mrs McCann would be required to return for more questioning, her status as a formal suspect became inevitable.

The family spokesman said: "Just before the session ended last night, they made it clear they had some further questions to ask which would require her to be in arguido status rather than just witness status."

Referring to Mrs McCann's condition the spokesman added: "She is shocked and surprised in several ways. First of all that such an accusation could be made against her.

"And obviously she is concerned that such a line of investigation can become a distraction from further attempts to find Madeleine."

Four-year-old Madeleine went missing from her family's flat in Praia da Luz back in May while her parents ate at a nearby tapas restaurant.