A leading child protection expert has said he has significant concerns about the man nicknamed "The Locator" who has been called in to help find Madeleine McCann.

Former detective Mark Williams-Thomas told Sky News Online he doubts the ability of Daniel Kruger to provide any assistance in tracking down the missing child.

Madeleine's parents, Kate and Gerry McCann, have given the South African some hair found on her clothing to use in his "missing person machine".

Mr Kruger refuses to reveal how his mysterious methods work, but they have apparently won him success and recognition in his homeland - which prompted the McCanns to call him in.

He said he has scoured Praia da Luz, in Portugal, and the surrounding area using the equipment, which he developed himself.

Not much is known about his "matter orientation system machine", but it is said to use satellite technology, and he has claimed he is currently in negotiations with companies to develop it.

The former policeman said he believed Madeleine was not transported beyond the area where she went missing on May 3, but her chances of being alive were "very slim".

It was reported he had uncovered a "forensic route" from Madeleine's holiday apartment, along paths and roads to a nearby beach where the trail went cold.

However, the university health and safety director was reluctant to talk in detail about his search, which was carried out over four nights in July.

And Mr Williams-Thomas told Sky News Online "The Locator's" claims belonged "in the realms of fantasy".

"Krugel has no published academic or scientific information about his machine, neither is there anything on the internet about it and no police force outside of his own country uses it," he said.

"If it really does locate missing people then not only would every police force purchase one, but he would be an acclaimed expert and millionaire.

"I am sure his intentions are honourable - however, there is no easy way to find Madeleine, no magic machine."

Madeleine, from Rothley, in Leicestershire, went missing from her family's holiday apartment while her parents dined nearby. She was three when she disappeared.