Police hope to harness the power of the internet to find Madeleine McCann.

Two new computerised images – one showing a tanned Madeleine with dark hair as if she had been living in the warmer climate of north Africa – have been created for the campaign.

The pictures form part of a one-minute film which officers hope people will spread around the world – in the first dedicated campaign of its kind – using blogs, e-mail and social networking sites such as Facebook and Twitter.

Officers at the Home Office-funded Child Exploitation and Online Protection (CEOP) centre, hope the campaign will prick the conscience of someone who knows where she is.

Parents Kate and Gerry, from Rothley, 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 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.

"We love Madeleine. Please help us bring her home."

The appeal is being targeted directly at a friend or relative of whoever kidnapped the youngster from Praia da Luz, Portugal, on May 3, 2007.

CEOP works with law enforcement agencies – including Leicestershire Constabulary and Interpol – to tackle child abuse.

CEOP head Jim Gamble said the clip's message had been crafted with the help of psychologists to persuade any 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."

He said the appeal came about after Madeleine's parents wrote to him expressing frustration that lines of inquiry were drying up.

He said: "We talked to psychologists about guilt, about how we can open the opportunity for an individual or remind them they can redeem themselves, they can do the right thing.

"It's about considering how normal people deal with keeping a secret and also how they can be prompted to come forward." CEOP has been involved in the search for Madeleine from the start. Early in the investigation, it asked tourists who visited Praia da Luz just before she vanished to send in holiday snaps to be compared against a database of images of criminals.

The US National Center for Missing and Exploited Children (NCMEC), which developed the age-progression images, released one in May to coincide with the second anniversary of her disappearance.

But following concerns that it looked "too American", fresh pictures have been created.

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 had spent time in the sunnier climate of southern Europe or north Africa.

In the voiceover to the video, Mr Gamble appeals directly to anyone with information.

He says: "We know 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.

"If you know who is involved and are keeping this secret, remember it is never too late to do the right thing."

Mr McCann said the video was targeting the abductor and the people who know that person and may have information.

He said: “I think this is targeted specifically to the abductor and the people that know that person and who may have information.

“As Jim says on the video, people may keep information out of misguided loyalty and very much we are trying to appeal to them and the abductor to do the right thing,” he said.

“And it is to try and get, I suppose, under their skin and prick their conscience.”

Any information will be passed to Leicestershire police, who will share it with detectives in Portugal.

www.ceop.police.uk