Manhattan’s top federal prosecutor said Friday that a judge lacks the authority to appoint a neutral expert to oversee the public release of documents in the sex trafficking probe of financier Jeffrey Epstein and British socialite Ghislaine Maxwell.

Judge Paul A. Engelmayer was told in a letter signed by U.S. Attorney Jay Clayton that he must reject a request this week by the congressional cosponsors of the Epstein Files Transparency Act to appoint a neutral expert.

U.S. Rep. Ro Khanna, a California Democrat, and Rep. Thomas Massie, a Kentucky Republican, say they have “urgent and grave concerns” about the slow release of only a small number of millions of documents that began last month.

In a filing to the judge they said they believed “criminal violations have taken place” in the release process.