LONDON — The Guardian newspaper says that London's Metropolitan Police Service stole the identities of dozens of dead children to use as aliases for undercover officers, learning the infants' personal histories and even issuing fake passports in their names.

The allegation is another potential embarrassment for U.K. law enforcement's undercover program, which has previously been rocked by revelations that police spies had sex with their targets and fathered children with activists.

Police said in a statement Monday that they were investigating the complaint and "appreciate the concerns that have been raised." It said the "practice referred to in the complaint is not something that would currently be authorized."

The Guardian based its story on two detailed accounts provided by former undercover officers, whom it did not identify by name.

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