Scotland Yard has identified a number of potential suspects who may have abducted Madeleine McCann, the force’s top detective revealed today.

Investigators carrying out a review of the case have drawn up a list of people who they say are “of interest” to the inquiry.

Detective Chief Superintendent Hamish Campbell, the head of Scotland Yard’s Homicide and Serious Crime Command, said there were a “good number” of individuals who should be questioned.

Today he urged the Portuguese authorities to investigate the new leads identified by the British review.

DCS Campbell, speaking on the eve of his retirement from the Met, said: “There are a lot of people of interest. There are people who could be properly explored further, if only to be eliminated.”

He refused to give numbers but said there was “more than a handful” of names of “people of interest”.

Madeleine was nearly four when she went missing from her family’s holiday apartment in Praia da Luz in Portugal in 2007 as her parents Kate and Gerry McCann dined with friends near-by.

The official Portuguese inquiry was shelved in 2008 but Scotland Yard launched a review of the case in 2011 after David Cameron responded to a plea from Madeleine’s parents.

Last year the review team led by Detective Chief Inspector Andy Redwood said it had identified 195 potential leads after examining a huge bundle of material.

Today DCS Campbell said the 30-strong review squad had done a “fantastic” job in identifying “further investigative and forensic opportunities.”

He said it was “perfectly probable” that information which could identify the suspect responsible for Madeleine’s disappearance was already within the Portuguese files.

He added: “We have to ask ourselves why are cases unsolved and, on many occasions, we find we passed the suspects by already and the suspect sits within our system.”

DCS Campbell said there were a “good number” of people who could be interviewed and eliminated to allow investigators to focus on a smaller group.

Detectives from the Yard’s team have travelled to Portugal around 10 times to liaise with the authorities there and gather evidence in an inquiry which has cost more than £2 million.

So far, Portugal’s attorney general has ruled out a new inquiry into Madeleine’s disappearance but the comments from the senior Yard detective will raise hopes of a fresh investigation.

DCS Campbell said: “The Portuguese hopefully will pursue some of these investigative opportunities with our assistance. There is room for further work and collaboration to resolve the case.”

He re-iterated a claim that Madeleine could still be alive. He said: “You only have to look at the case in Cleveland, Ohio, and the European cases. Of course, there is a possibility she is alive, you cannot exclude it. But the key is to investigate the case and, alive or dead, we should be able to try and discern what happened.”

He added: “The purpose of the review is to look at it with fresh eyes…there has been real benefit in doing it.”