Washington (CNN) The Justice Department inspector general told lawmakers Tuesday that he is unable to investigate the circumstances surrounding a 2008 plea deal reached between Labor Secretary Alex Acosta, then the US attorney in Miami, and Jeffrey Epstein, because of statutory limitations.

In a letter responding to Rep. Debbie Wasserman Schultz, a Florida Democrat, and other lawmakers, Michael Horowitz, the inspector general, said there were "important questions" about the resolution of the Epstein case, but lamented that allegations of misconduct relating to Justice Department attorneys' handling of litigation or legal decisions falls outside his purview.

"Over the past 30 years, my three predecessors as DOJ Inspector General and I have objected to this limitation on the OIG's jurisdiction because it shields prosecutorial misconduct from review by a statutorily independent OIG," Horowitz wrote.

Late last year the Miami Herald reported that Acosta negotiated the "deal of a lifetime" with accused pedophile Jeffrey Epstein in the late-2000s, allowing the well-connected Palm Beach billionaire to avoid a federal trial and serve only 13 months in prison.

The Herald first reported Horowitz's letter on Tuesday.

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