Internet users are being asked to help appeal to the conscience of a key witness who knows what happened to Madeleine McCann.
A one minute film has been released by British Police showing fresh images of how the missing youngster might look now. One picture features an older Maddie with darker hair and skin to show how her appearance could have changed if she had been living in North Africa.
The appeal, launched by the Child Exploitation and Online Protection (Ceop) centre, is targeted at a friend or relative of the person responsible for the little girl's disappearance.
Ceop head Jim Gamble said the clip's message, which has been translated into six other languages, had been crafted with the help of psychologists to persuade the witness to "do the right thing".
He said: "The person we are looking to reach is likely to be a partner, family member, friend or colleague of the person or people who were involved in Madeleine's disappearance. It is also highly probable that they, or someone close to them, is using the internet to search for any updates that may suggest the police are getting closer to discovering the truth."
Madeleine was nearly four when she disappeared from her family's holiday apartment in Praia da Luz in Portugal in May 2007. A massive international publicity drive was launched along with a major police investigation, but the youngster has never been found.
Madeleine's parents Kate and Gerry McCann, from Leicestershire, welcomed the initiative They said in a statement: "We are extremely grateful to Ceop for launching this new message around the world in such an effective way. It is vital that it is seen and heard as widely as possible.
"If you know what has happened to Madeleine, it is still not too late to do the right thing and come forward to your local police with that information. We love Madeleine. Please help us bring her home."
Ceop hopes people will spread the new film across the globe using blogs, email and social networking sites such as Facebook and Twitter.
It features a number of well-known photographs and video clips of Madeleine, as well as three pictures of how she could look now, aged six, if she is still alive.
In one her blonde hair and pale skin are unchanged, but in the second she has dark hair and skin to show how she might appear if she has spent time in the sunnier climate of southern Europe or north Africa.
The video has a voice-over in which Mr Gamble appeals directly to anyone with information about what happened to the child.
He says: "We know that there is someone out there who knows who is involved in her disappearance. They may be keeping this secret out of fear, misplaced loyalty or even love.
"Keeping this information secret only increases the anguish of Madeleine's family and friends and increases the risk to other children. If you know who is involved and are keeping this secret, remember that it is never too late to do the right thing."
The message is available in English, Arabic, French, German, Italian, Portuguese and Spanish. It is being supported by police agencies around the world, including Interpol, Europol and forces in Australia, the US, Canada and the United Arab Emirates.
Ceop said the appeal came about after Madeleine's parents, Kate and Gerry McCann, wrote to him expressing frustration that lines of inquiry were drying up.
Mr Gamble stressed that investigations involving missing children were never closed, citing the cases of youngsters such as Jaycee Lee Dugard, who turned up in California in August this year after disappearing 18 years earlier.He said: "For each one of those kids there's a story where lots of people thought they would never turn up again.
"I believe this is about hope, it's about collective hope. And I absolutely believe this message cascading and spreading in the right way will deliver answers for us."
Video: Watch the full interview with Kate and Gerry McCann
Video: Watch the Ceop appeal to find Madeleine McCann
