The couple, from Rothley, Leicestershire, recently marked the second anniversary of Madeleine going missing from their holiday flat in Praia da Luz, southern Portugal, on May 3, 2007, just days before her fourth birthday.
They will join families of other vanished youngsters tomorrow to mark International Missing Children’s Day.
The event on London’s South Bank will publicise the plight of the mothers and fathers left wondering what happened to their children many years after their disappearance.
The McCanns’ UK lawyer, Edward Smethurst, said the first step in their legal action will be to apply for a gagging order at Lisbon’s main civil court.
He said yesterday: “Proceedings are being issued as we speak.
“We’re applying for an injunction to prevent further publication of the book and anything to do with its contents.”
