'I don't know how long she will hold on for', says Kate McCann's anxious mother

She told a Portuguese magazine: 'What mother would not go insane if they lost a child?"

But the McCanns' spokesman was forced to deny that Mrs McCann was suicidal after the magazine headlined the article: "Kate's mother fears she will kill herself."

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Clarence Mitchell said: "It is beyond offensive to suggest Kate is suicidal. She is not.

"She is, however, a woman under immense pressure and her mother is perfectly entitled to defend her."

In the interview with 24 Horas, Susan Healy, 61, said: "I don't know how long she will hold on for.

"It doesn't seem like it but she has a very strong inner force. But with such cruelty, honestly I don't know - I don't know if any human can take such pressure."

She added: "Kate is an only child. If it was me, I'd die. But she can't let herself get so low.

"She has to think of her family, of Gerry and the twins.

"Sean and Amelie need their mother. But I'm afraid, I'm very afraid. I don't know how she's handling all this."

Mrs Healy, of Allerton, Merseyside, has spoken before of her worries for her daughter's health as she has endured the six-month investigation into Madeleine's disappearance. Other relatives have told how her family ensure the 39-year-old is never left alone and prepare her favourite meals to encourage her to eat properly.

Mrs McCann, a GP and devout Catholic, has weekly counselling sessions to help her cope, but has found it increasingly difficult to control her emotions.

The mother of three has told of "dark moments" and days when she cannot stop crying.

Friends say she is dreading Saturday, which marks the six-month milestone since Madeleine vanished.

The family has rallied round the couple since May 3, and Mrs Healy said she spoke to her daughter every day on the phone.

Mrs Healy said Gerry McCann, also 39, now kept the media coverage of the case away from his wife, in case it upset her, something she said she agreed with.

She said her daughter faced "a war" she could not win, adding: "People criticise her anyway.

"If she cries it's because she's faking, if she doesn't cry it's because she's cold.

"My God, there's no bigger pain in the world than to see a daughter suffer and to be accused or tried in the public square for something she did not do."

During the interview Mrs Healy frequently repeated her call for critics to be kinder to Mrs McCann, saying she was an excellent mother.

A friend said Mrs Healy's words had been "twisted" in the magazine's headline and added: "It's ludicrous and yet another horrible slur.

"Kate and Gerry are stunned at such an irresponsible report and twisting of words.

"Of course Kate is not suicidal. She has had so much to deal with but her priority is her family."

Mrs Healy last night denied she ever thought her daughter would commit suicide, saying: "Although Kate is under the most immense pressure, she would never, ever contemplate ending her life, for two reasons.

"One, she still wants to find Madeleine and, two, for the sake of her other two children."

David Cameron has said he feels "desperately sorry" for the McCanns. The Tory leader, whose daughter Nancy is three, the same age as Madeleine when she went missing, told the Mail on Sunday: "It must be awful not knowing what happened to your daughter and desperately wanting her back."