The parents of missing Madeleine McCann are the victims of a "witch-hunt" and there is no evidence to suggest they murdered their daughter, said Britain's former top police officer.
In an article for the News of the World, former Metropolitan Police chief Lord Stevens said there was no hard evidence because of the "sheer inadequacy" of the Portuguese police investigation.
He writes: "There's absolutely no chance that the parents of Madeleine McCann would be charged with her murder in this country. It would be an outrageous miscarriage of justice if they were.
"I've been a detective at the most senior level for 30 years and have never seen such a witch-hunt, or one based on such flimsy evidence."
He said Portuguese police should have immediately treated the McCanns as the prime suspects, adding: "That police error has become their tragedy now, because if they had been properly investigated back then they may well have been cleared."
He believed abduction was the most likely possibility.
Lord Stevens retired as Metropolitan Police commissioner in 2005 after five years in the post and more than 40 years in the force.
He then headed inquiries into the circumstances surrounding the death of Diana, Princess of Wales and alleged football bungs.
He was widely credited with transforming morale at Scotland Yard following the the Macpherson report into the Stephen Lawrence murder.
