Mayor de Blasio on Monday refused to weigh in on the concerns of good-government groups over the back-room selection of the next Bronx district attorney.

“Our focus now is on the work we have to do with the Bronx DA’s Office,” he said at an unrelated press conference at City Hall.

Bronx DA Robert Johnson is resigning to become a state Supreme Court judge in a move timed to allow the Bronx Democratic Party to pick the Democratic nominee who will almost certainly become his successor.

Critics say the process essentially lets political leaders rather than voters select the next district attorney.