The release by Portuguese police to British newspapers of previously unseen files on the disappearance of Madeleine McCann was "incomprehensible" and "upsetting", her family said.
The 2,000-page dossier detailed dozens of possible sightings of Madeleine after she disappeared from her family's holiday flat in Praia da Luz, southern Portugal, in May 2007, just before her fourth birthday.
A statement released by Kate and Gerry McCann said: "Disclosing such information publicly greatly jeopardises the search for Madeleine and puts witnesses and innocent members of the general public at risk (as well as causing them great anxiety). Release and publication of information in this manner also potentially compromises future investigations. It is difficult to see how anyone benefits from this week's actions."
One of the possible sightings was investigated by police in New Zealand after a girl resembling Madeleine was caught on CCTV in Dunedin, but it emerged Portuguese detectives failed to ask for a follow-up investigation.
Other leads in the newly released dossier include a report of a small blonde girl being dragged along the road to Faro airport in the Algarve - an hour's drive from Praia da Luz - on the night Madeleine vanished.
Another details how a young girl who looked like the missing child was seen being held at gunpoint on a French motorway by a half-naked man in August 2008.
The statement released by the McCanns, both 41 and from Rothley, Leicestershire, thanked their supporters.
It stated: "We are incredibly grateful to all those who continue to support us in our search for Madeleine.
"During weeks such as these, it is invaluable to know that we are not facing this difficult journey alone."
