The parents of missing Madeleine McCann are to launch a libel action against a Portuguese newspaper which claimed they killed their daughter.
Media speculation about Madeleine has been rife in Portugal
Last week, Tal & Qual reported that the "police believe" Kate and Gerry McCann killed her, with the paper suggesting Madeleine may have died in an accident.
The McCanns say they are "deeply hurt" by the allegations, but the paper says it stands by its sources for the story.
Police have stressed that the McCanns, of Rothley, Leics, are not suspects.
Four-year-old Madeleine vanished from a holiday apartment in Praia da Luz, Algarve, on 3 May while her parents were eating at a nearby restaurant.
Earlier this month the police said there were indications that Madeleine might have died.
The newspaper's front-page story, headlined "The police believe the parents killed Maddie", claimed the couple had either caused a fatal accident or given drugs to their daughter.
The allegations were attributed to a "source close to the investigation".
However, the director of police has said publicly that the McCanns have never been viewed as suspects.
Lawyers for the couple will file a seven-page defamation complaint against the journalist who wrote the article and the newspaper's director. The legal case says the story was completely untrue.
In a statement, lawyer Carlos Pinto de Abreu said the McCanns had already suffered "the most terrible trial that could happen to anyone" by not knowing what had happened to their daughter.
"The press has engaged in a horrific exercise in scandal-mongering, replete with rumours and lurid commentaries which are all aimed at one thing - to sell more TV time and newspaper space to advertisers," he said.
"Fortunately, so far only a few character-assassinating, tabloid-style outlets have gone beyond the limits of decency. Enough!"
He also called on institutions and members of society to "raise their voices against kidnappings and disappearances" and show "solidarity with the victims and their families".
Media speculation has been rife in Portugal since the police declared that Madeleine might have died.
Mr McCann said the couple had been "deeply hurt" by the report in Tal & Qual.
"We firmly believe that the report was speculative, defamatory and published despite official statements to the contrary, which is why we have instructed lawyers," he said.
He added: "Our daughter Madeleine was snatched from her bed on 3 May. She is still missing. The police have said time and time again we are not suspects. These are the facts.
"Everything else is at best speculation and in some cases downright lies."
But Emidio Fernando, the director of Tal & Qual and one of the two people named in the lawsuit, told BBC Radio 4's PM programme that he was not worried about the legal action.
"I'm completely tranquil with any possible lawsuit. I trust in my sources about that.
"We never accused Mr McCann or Mrs McCann. We just published one thing - the Portuguese police believe the Maddy parents [sic] killed Maddy by accident... just that."
The BBC's Steve Kingstone, who is in Praia da Luz, said the McCanns had previously held back from responding to the speculation, but now felt "a line had been crossed" and "enough was enough".
The newspaper's claim was based on the discovery of suspected traces of blood inside the family's apartment.
The UK's Forensic Science Service is continuing to analyse evidence recovered from the apartment.
Last week, Mr McCann asked the media to end the constant speculation about his daughter's whereabouts.
He said there had been "huge amounts written with no substance" and that it was not necessary to "bombard people on a daily basis" with Madeleine's image.