The Commissioner of the Metropolitan police yesterday revealed that he decided to take on the Madeleine McCann investigation because London’s falling murder rate meant that he had detectives spare.

Sir Paul said that Scotland Yard's experience and expertise meant that they were the perfect force to lead a review into the Portuguese investigation in Madeleine's disappearance Photo: AP

Sir Paul Stephenson has previously denied that Scotland Yard was forced to investigate the case by the Prime Minister and the Home Secretary.

The Commissioner has stressed that he made the decision and there was no political interference from David Cameron.

Yesterday, under questioning from Metropolitan Police Authority members, he detailed his reasoning for taking on the investigation.

Sir Paul said that one of the reasons is the number of murders in London – which has fallen to 124 in 2011 from 172 per year in 2006.

He explained that it meant there is now no need for 24 murder teams across the capital and the number will be reduced in the next nine months, leaving experienced detectives free to take on the McCann case.

Sir Paul also said that Scotland Yard’s experience and expertise meant that they were the perfect force to lead a review into the Portuguese investigation in Madeleine McCann’s disappearance during a family holiday in 2007.

Explaining the decision, he said: “It is about expertise. It is about the fact that we do have the capacity and the capability because we have decided to reduce the murder investigation teams.”

The Commissioner also faced accusations today that the Madeleine McCann case was getting "unfair" and "special" attention at Scotland Yard.

But he denied that his decision to agree to review the investigation into the girl's disappearance could come at the cost of other inquiries.

Sir Paul was confronted over the review by London Assembly member Jenny Jones. Speaking at City Hall, she said she sympathised with the McCann family but asked him: “Why is this a special case?”

Sir Paul replied: "I do not take your point." He added that other cases of missing people in London were reviewed every two years.

And he denied that it was unusual for the force to get involved in cases outside of its London jurisdiction, listing a number of cases including the Soham murders, the Jersey Child abuse case and the disappearance of Ben Needham, who vanished on a family holiday in Kos in 1991.

Sir Paul reiterated that the McCann review will not cost the Metropolitan Police. The Government will reimburse the Met on a quarterly basis as the review goes on, he said.

"It is not an open cheque and it is not going to go on forever," he added.