They hope the broadcast, which will be shown across the Iberian peninsula and North Africa, will reinvigorate the search for the missing girl.
The McCanns' investigators have set up a 24-hour hotline to accept calls, manned by operators able to speak several languages including English, Spanish, Arabic and Portuguese. It is the first time the McCanns have openly admitted that private investigators - illegal in Portugal during a police investigation - are working for them in other countries.
On Monday the couple gave interviews to Spain's three leading newspapers, saying there was a "very real possibility" their daughter has not been killed.
Mr McCann told El Mundo: "There is a very real possibility that Madeleine is alive and we want the police to look for her. The possibility that Madeleine is alive and in Spain is real. It is something we did not consider at the beginning, but now we are seriously weighing up. The border between the two countries is very big. If someone had a car, it is clear they could cross into Spain. There is no border guard and no one closed the border the night Madeleine disappeared." (Sky News)