Goncalo Amaral has already seen the book, Maddie: The Truth about the Lie, sell around 180,000 copies across Europe, and expects to sell tens of thousands more when the book is published in English.

The McCann's, confronted with news of this development, meanwhile admitted they would scrutinise the book with a view to taking legal action against the retired police detective.

Goncalo Amaral further told The Independent on Sunday, 'I have received numerous messages of support and solidarity since being taken off the case, including from the UK ' messages that also motivated me to tell people what I knew about the Maddie case. I am positive that there's also a section of the public eager to know the truth.

'People can form their opinion without the manipulation that we have seen before.'

He said his only regret was failing to carry out a reconstruction of the events soon after Madeleine vanished but claimed he was put under 'serious pressure' not to.

On whether he thought Madeleine was dead, he said: 'It is not just my opinion. A whole team of Portuguese and British investigators came to that conclusion last year, and this is part of the files. I have never said the couple killed their daughter and this is not my belief. Deaths may happen for natural reasons, accident or intervention by a third party.'

Back in August, Goncalo Amaral in comments to The Portugal News, said he regretted what he termed the premature closure of the investigation.

'In my opinion, a number of things are still lacking: We should have continued investigating the parents in order to either charge them or rule them out as suspects. If I represented this couple, I would have insisted that police investigations continue. Not everything we do is to incriminate a suspect. Often a phone will be tapped in order to obtain information that will clear a suspect.

We worked long hours discussing a number of potential explanations for Madeleine's disappearance; we did not insist solely that she had been abducted.'

As for a pending lawsuit over the publication of his book, the former detective said at the time, 'My book is based on facts. It could be a good occasion to take all the case files to court and compare what I wrote with that which is contained in the files.'

In a related development, the British Parliament is to delve into the effectiveness of press self-regulation, contempt of court, privacy and libel laws following the spate of settlements between the press, and the McCann family, the so-called Tapas Seven and former suspect Robert Murat.

A Select Committee will start investigations in the New Year and has invited leading newspapers to participate in the hearing.

The group will also study the effectiveness of the Press Complaints Commission.

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