Former Portuguese detective Goncalo Amaral today lost an attempt to overturn a ban on his book claiming that Madeleine McCann is dead, a spokeswoman for the child's parents said.
Kate and Gerry McCann welcomed the ruling by a judge at Lisbon's main civil court, saying they were "very pleased and relieved".
Mr Amaral was the first head of the police investigation into the girl's disappearance from Praia da Luz in Portugal in May 2007, shortly before her fourth birthday.
In July 2008 he published a book, Maddie: The Truth Of The Lie, which alleges that Madeleine died in her family's holiday flat and that her parents faked her abduction.
A judge granted the McCanns, both 41 and from Rothley, Leicestershire, a temporary injunction last September halting further sale or publication of Mr Amaral's book and a TV documentary he made about the case.
The ex-policeman launched an appeal against the ban last month, calling a series of witnesses to support his claims, but Judge Maria Gabriela Cunha Rodrigues rejected his challenge today.
Mr and Mrs McCann reacted to the ruling by vowing to continue looking for their daughter and appealing for help from the public.
They said in a statement: "We are very pleased and relieved with the judge's decision in Lisbon today.
"By upholding the injunction against Goncalo Amaral's book and DVD, the judge has rightly agreed that there has been significant, ongoing damage to the search for our beloved daughter Madeleine and to the rights of our family.
"We are grateful to the judge for accepting that this injustice must not continue.
"The court case has demonstrated, once again, that there is no evidence that Madeleine has come to any harm.
"It has also clearly shown that no police force is actively looking for Madeleine, even, shockingly, when they are presented with new information and leads.
"The motives of those who have tried to convince the world that Madeleine is dead, and who've disgracefully and falsely tried to implicate us in her disappearance, need to be seriously questioned.
"As painful and personally damaging as the slanderous claims of Mr Amaral and his supporters have been to us and our family, our primary focus has always been, and always will be, to find Madeleine through our own best investigative efforts.
"It is still incumbent upon the British and Portuguese authorities to ensure that every credible lead has been investigated and that a meaningful search for our innocent and vulnerable little girl is properly carried out.
"We must and will keep looking for Madeleine and those responsible for her abduction.
"We implore the public, especially the Portuguese people, to help us look for Madeleine, to remain vigilant and to give us any information that could help us find our daughter."
Mr Amaral's lawyers argued that the material in his book was contained in the official Portuguese police files for the investigation, many of which were made public when the case was shelved in August 2008.
The McCanns say their main motive for challenging the former policeman is the fear that people will stop looking for Madeleine if they think she is dead.
The couple are also seeking 1.2 million euros (£1.08 million) in compensation for defamation in separate civil proceedings against Mr Amaral in Portugal.
Speaking before today's ruling, the former detective vowed to fight all the way to the European Court of Human Rights if he lost.
Mr and Mrs McCann are due to respond to the judgment in person at a press conference in London tomorrow.