New York City Mayor Bill de Blasio announced on Thursday that he has retained a prominent criminal defense lawyer to help him cooperate with state and federal corruption probes surrounding City Hall and his 2013 campaign.

The lawyer, Barry Berke of the Manhattan firm Kramer Levin Naftalis & Frankel, was previously retained to represent de Blasio’s campaign, and will continue in that role. He is a de Blasio appointee to the Lincoln Center board of directors.

A statement from a de Blasio spokesman said Berke would act as “his attorney to assist in all efforts to cooperate with authorities and ensure they have all the information they need to bring these investigations to a prompt conclusion.”

City Hall has been besieged by reports that U.S. Attorney Preet Bharara’s office has been investigating possible city favors for donors ranging from developers to foes of Central Park horse carriages, and the lifting of use restrictions on a health facility after its sale to a connected developer.

Bharara has also been probing NYPD corruption, and a separate state-federal probe is looking into de Blasio’s efforts to funnel big contributions to Democratic state Senate campaigns. Subpoenas were served on City Hall last week.

Berke is not expected to be paid with city funds, but in another announcement on Thursday city Corporation Counsel Zachary Carter said he was hiring outside legal help to manage subpoenas and document requests related to the probes.

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“As part of our cooperation with law enforcement inquiries, the Law Department has contracted with the law firms Debevoise & Plimpton as well as Carter Ledyard & Milburn to represent the City and assist in document collection and review,” a spokesman said in a statement. “The lawyers have been in touch with the U.S. attorney’s office to advance that cooperation.”

Debevoise and Carter Ledyard are two of Manhattan’s priciest top-tier law firms, but the law department had no estimate how much it will cost or how long it will take to compile documents.