Madeleine McCann's body was dumped at sea, a former Portuguese police chief claims in a novel about the case.
In Paulo Cristovao's fictional account the little girl's disappearance is never solved.
But Kate and Gerry McCann's spokesman accused the ex-inspector - who never worked on the case - of trying to profit from the couple's misfortune, saying his claims were "hurtful and distressing".
Cristovao's novel, The Star Of Madeleine, follows two fictional police officers as they attempt to unravel the mystery.
They end their investigation staring out at the Atlantic Ocean and the case remains unsolved - an outcome the McCanns have described as their worst nightmare.
Cristovao has been a constant critic of the McCanns, and previously called for them to be arrested for leaving their children alone in their Algarve holiday apartment on the night Madeleine vanished in May last year.
At the novel's launch in Portugal, he made no apology for the anguish the story might cause, saying: "I am sure Madeleine's parents will not like the book."
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Cristovao stopped short of accusing the couple, of Rothley, Leicestershire, saying: "In their shoes, I'd behave in exactly the same way as they did during the investigation.
"I would defend myself with all the weapons that I could use. The difference in this world is that some have more weapons than others."
But their spokesman, Clarence Mitchell, said: "It is a great pity that people still feel the need to profit out of Madeleine's disappearance.
"That is very distressing for Kate and Gerry.
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"The efforts that people are putting into this kind of profiteering would be better spent helping the investigation to find Madeleine.
"If Mr Cristovao feels he has any information relevant to that search then we would ask him to help with that investigation.
"Beyond that we won't dignify these so-called books with a comment."
Cristovao said his book was "pro-Portugal" and it contains thinly veiled criticism of Britain's political involvement in the case.
In the novel the police officers face pressure from British diplomats as they try to unravel the mystery.
In reality, Portuguese police have criticised Gordon Brown's decision to raise the investigation in meetings with his Portuguese counterpart, and have hit out at political interference.
Cristovao worked for the Policia Judiciaria for several years, on cases including the hunt for missing nineyearold Joana Cipriano, who disappeared in 2004, from Figueira, just seven miles from Praia da Luz.
Her body has never been found. Her mother Leonor was later accused and convicted of her murder, but has since claimed that police beat her into making a confession.
Cristovao and three others have been accused of torturing her.
The disgraced former head of the Madeleine inquiry, Goncalo Amaral, has denied claims that he covered up the torture.
Cristovao, who left the force following the case, has also written about a book about it, called The Star Of Joana.
Mrs Cipriano, 36, and her brother Joao were jailed for 16 years for the murder but her lawyer hopes to overturn the conviction at the European Court of Human Rights.
There have been several books published in Portugal about Madeleine, who vanished days before her fourth birthday.
The majority have been critical of the McCanns' decision to leave their children alone in their holiday apartment while they dined with friends.
Some have suggested they could have been involved in Madeleine's disappearance.