Goncalo Amaral revealed he has completed the work, which re-examines the timeline of Madeleine’s disappearance. He is now seeking to publish it.
Mr Amaral co-ordinated the original investigation in Portugal and went on to publish a book making unfounded allegations against the McCanns.
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The couple fiercely rebuked his claims and the book was withdrawn.
But last month Mr Amaral won an appeals court case in Portugal’s capital Lisbon, allowing the book to be published.
Now he says that he has penned a second book about the disappearance which he is planning to publish.
The move will anger Kate and Gerry, who have spent the past nine years searching for their daughter who disappeared on May 3, 2007, then aged three, from the family’s holiday apartment in the Algarve resort of Praia da Luz.
Mr Amaral was removed as the head of the Madeleine investigation in 2008 after he criticised British detectives’ handling of the case.
He went on to write The Truth Of The Lie, a controversial book which Kate McCann described as “devastating and painful” to the family, and which she said could adversely affect the investigation.
The McCanns are now taking the case to the Supreme Court in Lisbon, where divorcee Mr Amaral, 47, lives, hoping to overturn the appeal.
Mr Amaral, now retired, said he bore no ill will against the McCanns, but revealed he had completed a second book.
He said: “Winning the appeal case gives me no joy or happiness. It is just part of the legal process.
Winning the appeal case gives me no joy or happiness
“I will defend my reputation, and the integrity of the officers who worked with me, in the courts but I just want a quiet peaceful life.
“I am pleased I have a court ruling which defends the freedom of expression.
Madeleine McCann sightings
“I was invited to book signings now the book is back on sale but I turned them down. I don’t want to be in the spotlight.
“I have written another book, examining the timeline and what people have said, and I am looking to publish that.
“I enjoy writing books and relaxing and I will continue to do that.”