Martin Brunt, speaking from the police investigators' base in Faro, described the move as a "breakthrough" in the investigation.

He said: "We don't know exactly where the digging will take place and it's not an operation that's being launched on new information.

"It appears that there is information that was given to the Portuguese over the past seven years that indicated that there might be evidence to be found at certain locations.

"We think one of them may be the beach area and another may be around the apartments where Madeleine was last seen.

"It is a breakthrough and it really will launch a new phase in the investigation because this will be the first time that we will see Scotland Yard officers on the ground, not just talking to Portuguese police but working with them in the search for perhaps more tangible evidence."

Last week, Kate McCann said she needs to know what happened to her daughter even if it was the "worst case scenario".

She said: "Madeleine's either alive or she isn't and we can't change that.

"Obviously our hope is that she's alive and being well looked after but regardless of the outcome, we need to know. We all need to know."

Madeleine disappeared from the apartment she was staying in with her parents and two siblings on May 3, 2007. She was three years old at the time she vanished.