Photo: Reuters

HE family of missing English girl Madeleine McCann are aiming to reach 80 per cent of the world's inboxes in two weeks with a viral email and photo reminding people of her disappearance.

The picture shows the distinctive imperfection in her right eye which her parents hope could be the vital clue to her discovery.

Madeleine, aged four at the time, went missing four years ago next month while the family were holidaying in Praia da Luz in Portugal.

Her aunt Phil McCann said: ''I am asking everyone I know to send this as a chain letter as the story is only being covered in Britain, Eire and Portugal. We don't believe she is in Portugal any more.'' Another aunt, Diane McCann, said: ''The purpose of this is to highlight the distinction in Madeleine's eye where the pupil runs into the blue-green iris.'' She said Madeleine's hair could be cut or dyed.

Maddie disappeared from her bed as her parents Gerry and Kate dined in their holiday complex.

Publication of a book about their daughter's disappearance has been delayed to avoid clashing with the royal wedding on April 29.

All proceeds from the book will go to the McCanns' official search fund.