The couple, who fear the Portuguese police have all but given up the search, have asked Control Risks Group to mount a fresh hunt. The firm, which has long experience of kidnappings and search and rescue operations, is understood to have a small team in Portugal already.
The McCanns also want investigations carried out wherever there have been credible sightings.
The development came as:
• It was revealed that two separate witnesses reported seeing Madeleine in Marrakesh, Morocco, on the same day;
• A double-glazing magnate who made a fortune from Everest windows pledged to bankroll the McCanns;
• British forensic scientists angrily criticised Portuguese police for "overinterpreting" DNA results.
Control Risks was founded in 1975, initially to help businessmen in South America who were targeted by kidnappers. It claims to have solved more than 1,000 cases.
It has 600 employees, many of them former Special Forces members or MI6 agents. Ex-SAS commander Sir Michael Rose is a director.