McCann twins pick up the phone every day to ask 'Where are you Madeleine?

Gerry McCann's mother Eileen described how twins, Sean and Amelie, now three, are a constant heartbreaking reminder for their parents because they still ask for Madeleine every single day.

Mrs McCann, 67, also praised Kate McCann for struggling to give her two other children a normal life but admitted this was simply not possible with Madeleine still missing.

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The retired book-keeper said: 'Kate and Gerry don't have to remind their twins that Madeleine is no longer there, because they ask where she is all the time.

'They pick up the phone to speak to her and ask 'Where are you?'

She adds: 'Kate is a very capable mother. She is trying to keep life normal for the twins. She tales them to playgroups twice a week. But they are just not a family unit without Madeleine.'

Gerry's mother insists she was always certain Madeleine, then three, was abducted from the couple's holiday apartment in Praia da Luz in the Algarve.

She told the Sun: 'Somebody came into Maddie's room, carried her out in her pyjamas and we just don't know where she is. It's the stuff of nightmares. Whoever did this is a monster.'

Her comments came as it emerged the McCanns are planning to write a book about their 'year of hell' without their daughter.

Publishing sources say they could be paid up to £1million.

The couple's spokesman, Clarence Mitchell, stressed they wanted to raise money for the dwindling Find Madeleine appeal and to counter a campaign of smears by Portuguese police.

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Several publishers have approached them and there is every possibility of a bidding frenzy.

Last week it emerged that the former head of the Madeleine investigation, Goncalo Amaral, has written a book about the case with the working title The Truth of the Lie.

Insiders said it will contain 'explosive' details about the police inquiry and the decision to name the McCanns as official suspects, or arguidos.

Mr Mitchell confirmed that Mr McCann, 39, had talked to one publishing house and been approached by several others.

He said: 'The idea of writing an official book at some point is appealing. It's a legitimate way of raising money for the fund but would also give them a chance to put across their side of the story, and to talk about some of the wider issues.'

Scott Pack, former head of buying for Waterstone's, said: 'A book could go for a million. There is a feeling that we know everything there is to know about this story but the public are still fascinated.'

But publisher Patrick Jenson-Smith said it could be difficult to sell 'a story without a conclusion'. The McCanns have considered a series of ways to fund their continuing search for Madeleine, who disappeared from their holiday apartment in Praia da Luz, Portugal, almost a year ago.

The little girl, then three, had been left with her two-year- old twin brother and sister while their parents went out for dinner nearby.

The couple suffered a public backlash when it emerged that their representatives had begun negotiations with the giant IMG entertainment agency over selling the film rights to their story. There were also discussions on bids from the Oprah Winfrey and Barbara Walters U.S. TV shows.

The McCanns, of Rothley, Leicestershire, are desperate to raise money for the Find Madeleine fund amid fears that £1.2million raised in donations from the public will run out within months.

The independent television production company Mentorn Media has made a £10,000 donation to the fund in return for the couple's cooperation with a two-hour documentary to be shown on ITV1 on Wednesday.

In the film, GP Mrs McCann, 40, speaks of her renewed hope that Madeleine is still alive but admitted that sometimes she was ' desperate' and considered giving up.

She said: 'It is pure torture to deal with and it has been a long year of hell.

'You have days when you're so down and desperate and tired. You think you've got to switch off and think, okay, we've tried really hard and we've come up with nothing and now we need to make the best of what we've got.

'We're never going to hit that day. It doesn't matter how small the possibility is [of Madeleine being found alive], the possibility is still there.'

Mrs McCann also told how their twins Sean and Amelie, now three, used their toy phones to try to 'call' Madeleine and played games where they try to find her.