The Historic Districts Council, which can influence the city’s decisions but has no official role, has come out in opposition to the Frick Collection’s planned expansion, the council announced on Wednesday.

The council’s public review committee — which examines proposals for work on landmark buildings that are to come before the Landmarks Preservation Commission — said in a statement that the proposed expansion “will destroy the design intent of Thomas Hastings’ residential composition and John Russell Pope’s graceful museum transformation.”