Met chief: Madeleine McCann could still be found alive

Madeleine McCann could still be alive, Britain's most senior police officer has said.

Sir Paul Stephenson said it was right for Scotland Yard to agree to Home Secretary Theresa May's request for help, and said there was "always a chance" that the missing girl could be found.

His comments came after the decision to involve the Metropolitan Police was described as a "ludicrous" move that would deny other victims of crime the chance of justice while using up valuable police resources.

But Sir Paul told a London radio station it was not unique for the Met to lend its expertise in difficult cases outside of its jurisdiction - a team was sent to Antigua in 2008 to help investigate the murders of honey-mooners Ben and Catherine Mullany, and two years ago Scotland Yard was asked to help Jersey police investigate the disappearance of two people who had been missing since the 1980s.

"There is always a chance," he said. "When you receive a request, supported by the Prime Minister, from the Home Secretary, you take that very seriously. On balance, I think it was the right thing to do."

But the review, which will be funded by the Home Office, has sparked fierce criticism. Last week, Lord Harris, a member of the Metropolitan Police Authority, said: "Whilst no one doubts the desirability of doing what can sensibly be done to find out what has happened to Madeleine McCann, I can imagine that the senior leadership of the Metropolitan Police are not exactly happy about this.

"It again embroils their officers in a high-profile investigation, where the chances of success are unclear and which will divert limited investigative resources away from other matters."

Madeleine went missing from her family's holiday flat in the Algarve on 3 May, 2007.